高负载量原子级催化剂的合成

Catalyst systems populated by high-density single atoms are crucial for improving catalytic activity and selectivity, which can potentially maximize the industrial prospects of heterogeneous single-atom catalysts (SACs). However, achieving high-loading SACs with metal contents above 10 wt% remains challenging. Here we describe a general negative pressure annealing strategy to fabricate ultrahigh-loading SACs with metal contents up to 27.3–44.8 wt% for 13 different metals on a typical carbon nitride matrix. Furthermore, our approach enables the synthesis of high-entropy single-atom catalysts (HESACs) that exhibit the coexistence of multiple metal single atoms with high metal contents. In-situ aberration-corrected HAADF-STEM (AC-STEM) combined with ex-situ X-ray absorption fine structure (XAFS) demonstrate that the negative pressure annealing treatment accelerates the removal of anionic ligand in metal precursors and boosts the bonding of metal species with N defective sites, enabling the formation of dense N-coordinated metal sites. Increasing metal loading on a platinum (Pt) SAC to 41.8 wt% significantly enhances the activity of propane oxidation towards liquid products, including acetone, methanol, and acetic acid et al. This work presents a straightforward and universal approach for achieving many low-cost and high-density SACs for efficient catalytic transformations. High-density single atom catalysts are crucial for improving catalytic performance but achieving metal contents above 10 wt% is challenging. Here, authors develop a negative pressure annealing strategy, which enables fabrication of catalysts with metal contents up to 27–45 wt% for 13 different metals.

Metal single-atom catalysts (M-SACs) attract extraordinary attention for promoting oxygen reduction reaction (ORR) with 100% atomic utilization. However, low metal loading (usually less than 2 wt%) limits their overall catalytic performance. Herein, a hierarchical-structure-stabilization strategy for fabricating high-loading (18.3%) M-SACs with efficient ORR activity is reported. Hierarchical pores structure generated with high N content by SiO2 can provide more coordination sites and facilitate the adsorption of Fe3+ through mesoporous and confinement effect of it stabilizes Fe atoms in micropores on it during pyrolysis. High N content on hierarchical pores structure could provide more anchor sites of Fe atoms during the subsequent secondary pyrolysis and synthesize the dense and accessible Fe-N4 sites after subsequent pyrolysis. In addition, Se power is introduced to modulate the electronic structure of Fe-N4 sites and further decrease the energy barrier of the ORR rate-determining step. As a result, the Fe single atom catalyst delivers unprecedentedly high ORR activity with a half-wave potential of 0.895 V in 0.1 M KOH aqueous solution and 0.791 V in 0.1 M HClO4 aqueous solution. Therefore, a hierarchical-pore-stabilization strategy for boosting the density and accessibility of Fe-N4 species paves a new avenue toward high-loading M-SACs for various applications such as thermocatalysis and photocatalysis.

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Fe single-atom catalysts (h3-FNCs) with high loading, high catalytic activity and high stability were synthesized via a method capable of increasing both the metal loading and mass-specific activity by exchanging zinc with iron. The “density effect,” derived from the sufficiently high density of active sites, has been discovered for the first time, leading to a significant alteration in the intrinsic activity of single-atom metal sites. The superior oxidase-like catalytic performance of h3-FNCs ensures highly effective bacterial eradication. Fe single-atom catalysts (h3-FNCs) with high loading, high catalytic activity and high stability were synthesized via a method capable of increasing both the metal loading and mass-specific activity by exchanging zinc with iron. The “density effect,” derived from the sufficiently high density of active sites, has been discovered for the first time, leading to a significant alteration in the intrinsic activity of single-atom metal sites. The superior oxidase-like catalytic performance of h3-FNCs ensures highly effective bacterial eradication. The current single-atom catalysts (SACs) for medicine still suffer from the limited active site density. Here, we develop a synthetic method capable of increasing both the metal loading and mass-specific activity of SACs by exchanging zinc with iron. The constructed iron SACs (h3-FNC) with a high metal loading of 6.27 wt% and an optimized adjacent Fe distance of ~ 4 Å exhibit excellent oxidase-like catalytic performance without significant activity decay after being stored for six months and promising antibacterial effects. Attractively, a “density effect” has been found at a high-enough metal doping amount, at which individual active sites become close enough to interact with each other and alter the electronic structure, resulting in significantly boosted intrinsic activity of single-atomic iron sites in h3-FNCs by 2.3 times compared to low- and medium-loading SACs. Consequently, the overall catalytic activity of h3-FNC is highly improved, with mass activity and metal mass-specific activity that are, respectively, 66 and 315 times higher than those of commercial Pt/C. In addition, h3-FNCs demonstrate efficiently enhanced capability in catalyzing oxygen reduction into superoxide anion (O2·−) and glutathione (GSH) depletion. Both in vitro and in vivo assays demonstrate the superior antibacterial efficacy of h3-FNCs in promoting wound healing. This work presents an intriguing activity-enhancement effect in catalysts and exhibits impressive therapeutic efficacy in combating bacterial infections.

High‐temperature pyrolysis (HTP, ≥900 °C) is a widely used method for synthesizing single‐atom catalysts (SACs). However, the high operational temperatures required for HTP pose significant challenges in achieving high single‐atom loading, primarily due to the Ostwald ripening effect. In this work, a low‐temperature trans‐metalation synthesis approach is developed which involves the exchange of cation between transition metal ions (M = Fe, Co, Cu, Ni, Mn, etc) and Zn2+ ions on a nitrogen‐doped carbon (NC) matrix within a molten salt medium. This strategy effectively avoids phase transformations and enables the direct formation of high mass loading (3.7–4.7 wt.%) of atomically dispersed M‐N4 sites. Both experimental and theoretical analyses confirm that this cation‐exchange occurs at a lower temperature threshold of 450 °C, significantly reducing the energy barriers for SACs synthesis. Furthermore, the synthesized catalyst with atomically dispersed Fe sites demonstrate excellent performance toward oxygen reduction reaction and fuel cell with a peak power density of 1.12 W cm−2 in an H2─O2 fuel cell at 1.0 bar and 80 °C.

The development of efficient oxygen reduction reaction (ORR) catalysts is critical for advancing rechargeable metal‐air batteries. While single‐atom iron catalysts (Fe‐SACs) are promising platinum alternatives, a major synthesis challenge lies in achieving high metal loading without sacrificing atomic dispersion. Here, a high‐loading (7.0 wt.%) iron single‐atom catalyst (P─Fe─N/C) synthesized via a phosphoric acid‐assisted approach is presented. This innovative method involves the carbonization of a nitrogen‐doped carbon precursor derived from ZIF‐8, pre‐loaded with Fe 3 ⁺ and phosphoric acid. This strategy facilitates the simultaneous achievement of dense atomic Fe dispersion and phosphorus incorporation within the carbon matrix. The incorporated phosphorus elevates the spin state of the Fe centers, disrupting the symmetry of the electronic density of states at high‐density Fe sites, a critical factor for enhanced O 2 activation. Consequently, P─Fe─N/C exhibits exceptional oxygen reduction reaction (ORR) activity, achieving a half‐wave potential of 0.905 V (vs RHE) in alkaline media, as corroborated by modeling and kinetic studies. Notably, this catalyst enables high‐performance liquid and solid‐state zinc‐air batteries, delivering high power densities and exceptional operational stability. This work not only showcases an advanced catalyst but also proposes a generalizable methodology for the development of high‐loading single‐atom catalysts.

Single-atom catalysts (SACs) have attracted significant attention for peroxymonosulfate (PMS) activation in advanced oxidation processes, yet their practical application is limited by the lack of simple synthesis routes that enable high metal loading and controlled electronic environments with broad pH adaptability. Here, we report a one-step strategy to construct Co3(HITP)2 (HITP=2,3,6,7,10,11-hexaiminotriphenylene), a Co-N4 SAC with a Co loading of 9.97 wt%. The π-d conjugated HITP ligands provide a highly delocalized electronic environment that precisely modulates the catalytic centers. The catalyst achieved nearly complete degradation of carbamazepine (CBZ) in a continuous-flow reactor, highlighting its efficiency and stability. Mechanistic investigations showed that PMS activation proceeds via the generation of sulfate radicals (SO4•-) and singlet oxygen (1O2) in comparable yields. Density functional theory (DFT) calculations revealed that preferential adsorption of the terminal oxygen atom of PMS on Co sites is the key step initiating the formation of SO4•-, SO3•-, and subsequently 1O2. This work provides molecular-level insights into the fabrication of delocalized SACs and offers a promising pathway toward efficient catalytic water purification technologies.

Singlet oxygen (1O2) is an excellent active species for the selective degradation of organic pollutions. However, it is difficult to achieve high efficiency and selectivity for the generation of 1O2. In this work, we develop a graphitic carbon nitride supported Fe single-atoms catalyst (Fe1/CN) containing highly uniform Fe-N4 active sites with a high Fe loading of 11.2 wt%. The Fe1/CN achieves generation of 100% 1O2 by activating peroxymonosulfate (PMS), which shows an ultrahigh p-chlorophenol degradation efficiency. Density functional theory calculations results demonstrate that in contrast to Co and Ni single-atom sites, the Fe-N4 sites in Fe1/CN adsorb the terminal O of PMS, which can facilitate the oxidization of PMS to form SO5•-, and thereafter efficiently generate 1O2 with 100% selectivity. In addition, the Fe1/CN exhibits strong resistance to inorganic ions, natural organic matter, and pH value during the degradation of organic pollutants in the presence of PMS. This work develops a novel catalyst for the 100% selective production of 1O2 for highly selective and efficient degradation of pollutants.

The oxygen reduction reaction (ORR) which is the cathodic reaction in many electric energy generators such as fuel cells, Li-air batteries and Zn-air batteries, requires a catalyst to enhance the...

Metal single-atom catalysts (M-SACs) have emerged as an attractive concept for promoting heterogeneous reactions, but the synthesis of high-loading M-SACs remains a challenge. Here, we report a multilayer stabilization strategy for constructing M-SACs in nitrogen-, sulfur- and fluorine-co-doped graphitized carbons (M = Fe, Co, Ru, Ir and Pt). Metal precursors are embedded into perfluorotetradecanoic acid multilayers and are further coated with polypyrrole prior to pyrolysis. Aggregation of the metals is thus efficiently inhibited to achieve M-SACs with a high metal loading (~16 wt%). Fe-SAC serves as an efficient oxygen reduction catalyst with half-wave potentials of 0.91 and 0.82 V (versus reversible hydrogen electrode) in alkaline and acid solutions, respectively. Moreover, as an air electrode in zinc–air batteries, Fe-SAC demonstrates a large peak power density of 247.7 mW cm−2 and superior long-term stability. Our versatile method paves an effective way to develop high-loading M-SACs for various applications. Metal single-atom catalysts offer great potential in bridging the gap between heterogeneous and homogeneous catalysis. Here the authors demonstrate a multilayer stabilization strategy for fabricating high-loading single-atom catalysts including non-precious and noble metals.

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The poor electrochemical reaction kinetics of Li polysulfides is a key barrier that prevents the Li-S batteries from widespread applications. Ni single atoms dispersed on carbon matrixes derived from ZIF-8 are a promising type of catalyst for accelerating the conversion of active sulfur species. However, Ni favors a square-planar coordination that can only be doped on the external surface of ZIF-8, leading to a low loading amount of Ni single atoms after pyrolysis. Herein, we demonstrate an in situ trapping strategy to synthesize Ni and melamine-codoped ZIF-8 precursor (Ni-ZIF-8-MA) by simultaneously introducing melamine and Ni during the synthesis of ZIF-8, which can remarkably decrease the particle size of ZIF-8 and further anchor Ni via Ni-N6 coordination. Consequently, a novel high-loading Ni single-atom (3.3 wt %) catalyst implanted in an N-doped nanocarbon matrix (Ni@NNC) is obtained after high-temperature pyrolysis. This catalyst as a separator modifier shows a superior catalytic effect on the electrochemical transitions of Li polysulfides, which endows the corresponding Li-S batteries with a high specific capacity of 1232.4 mA h g-1 at 0.3 C and an excellent rate capability of 814.9 mA h g-1 at 3 C. Furthermore, a superior areal capacity of 4.6 mA h cm-2 with stable cycling over 160 cycles can be achieved under a critical condition with a low electrolyte/sulfur ratio (8.4 μL mg-1) and high sulfur loading (4.85 mg cm-2). The outstanding electrochemical performances can be attributed to the strong adsorption and fast conversion of Li polysulfides on the highly dense active sites of Ni@NNC. This intriguing work provides new inspirations for designing high-loading single-atom catalysts applied in Li-S batteries.

A zinc (Zn)‐based single‐atom catalyst (SAC) is recently reported as an active Fenton‐like catalyst; however, the low Zn loading greatly restricts its catalytic activity. Herein, a molecule‐confined pyrolysis method is demonstrated to evidently increase the Zn loading to 11.54 wt.% for a Zn SAC (ZnSA‐N‐C) containing a mixture of Zn−N4 and Zn−N3 coordination structures. The latter unsaturated Zn−N3 sites promote electron delocalization to lower the average valence state of Zn in the mix‐coordinated Zn−Nx moiety conducive to interaction of ZnSA‐N‐C with peroxydisulfate (PDS). A speedy Fenton‐like catalysis is thus realized by the high‐loading and low‐valence ZnSA‐N‐C for PDS activation with a specific activity up to 0.11 min L−1 m−2, outstripping most Fenton‐like SACs. Experimental results reveal that the formation of ZnSA‐N‐C−PDS* complex owing to the strong affinity of ZnSA‐N‐C to PDS empowers intense direct electron transfer from the electron‐rich pollutant toward this complex, dominating the rapid bisphenol A (BPA) elimination. The electron transfer pathway benefits the desirable environmental robustness of the ZnSA‐N‐C/PDS system for actual water decontamination. This work represents a new class of efficient and durable Fenton‐like SACs for potential practical environmental applications.

Single-atom catalysts (SACs) as a bridge between hetero- and homogeneous catalysis have attracted much attention. However, it is still challenging to generate stable single atoms with high metal loadings and the application of SACs in more traditionally homogeneous catalytic reactions are highly desirable. Herein, coordinatively unsaturated Al2O3 supportedCu SAC with a high Cu loading of 8.7 wt% was prepared and firstly used in the amine-free synthesis of homoallylboranes. Up to 99% conversion and 95% 1,4-selective boration of the enals and 48-68% isolated yields of homoallylboranes were achieved, equaling to those of reported homogenous catalysts and more efficient and stable than nano Cu/γ-Al 2 O 3 . Mechanistic investigation indicated that Cu-Bpin species are the active intermediates of selective boration. The superior catalytic and recycling performance of Cu SAC paves an efficient and green path toward selective synthesis of homoallyborane fine chemicals.

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Electrocatalytic CO2-to-CH4 conversion provides a promising means of addressing current carbon resource recycling and intermittent energy storage. Cu-based single-atom catalysts have attracted extensive attention owing to their high intrinsic activity toward CH4 production; however, they suffer from uncontrollable metal loading and aggregation during the conventional pyrolysis process of carbon-based substrates. Herein, we developed a pyrolysis-free method to prepare a single-atom Cu catalyst anchored on a formamide polymer substrate with a high loading amount and well atomic dispersion through a mild polycondensation reaction. Owing to the isolation of copper active sites, efficient CO2-to-CH4 conversion is achieved over the single-atom Cu catalyst, along with the significant suppression of C-C coupling. As a result, the optimal single-atom catalyst with 5.87 wt% of Cu offers high CH4 faradaic efficiencies (FEs) of over 70% in a wide current density range from 100 to 600 mA cm-2 in the flow cell, together with a maximum CH4 partial current density of 415.8 mA cm-2. Moreover, the CH4 FE can reach 74.2% under optimized conditions in a membrane electrode assembly electrolyzer. This work provides new insights into the subtle design of highly efficient electrocatalyst for CO2 reduction.

Single-atom catalysts (SACs) have shown great promise for electrocatalytic applications such as the oxygen evolution reaction (OER). However, the high surface free energy of the isolated metal sites in SACs results in a generally low metal loading, which limits the density of active sites. Herein, we constructed low- and high-loading SACs on a γ-graphyne (GY) support using a series of transition metals (Fe, Co, Ni, Cu, Rh, Pd, Ag, Ir, and Pt) to study their OER performance. Calculations demonstrate that a high metal loading reduces the OER overpotential of Fe- and Co-GY catalysts, especially for Fe-GY, which shows exceptional activity with an overpotential of only 0.39 V. Notably, the bonding and anti-bonding stabilized energy difference (BASED) analysis indicates that the high loading Fe-GY optimizes the binding strength of *OH and *O intermediates, thereby lowering the overpotential of the rate-determining step (*OH → *O). This change is attributed to the synergy between adjacent Fe atoms, which modifies the charge distribution at the Fe sites, as shown by differential charge and density of states (DOS) analyses. Our findings help pave the way for the rational design of high-loading SACs for electrocatalysis.

Designing single‐atom catalysts (SACs) with high density of accessible sites by improving metal loading and sites utilization is a promising strategy to boost the catalytic activity, but remains challenging. Herein, a high site density (SD) iron SAC (D‐Fe‐N/C) with 11.8 wt.% Fe‐loading is reported. The in situ scanning electrochemical microscopy technique attests that the accessible active SD and site utilization of D‐Fe‐N/C reach as high as 1.01 × 1021 site g−1 and 79.8%, respectively. Therefore, D‐Fe‐N/C demonstrates superior oxygen reduction reaction (ORR) activity in terms of a half‐wave potential of 0.918 V and turnover frequency of 0.41 e site−1 s−1. The excellent ORR property of D‐Fe‐N/C is also demonstrated in the liquid zinc‐air batteries (ZABs), which exhibit a high peak power density of 306.1 mW cm−2 and an ultra‐long cycling stability over 1200 h. Moreover, solid‐state laminated ZABs prepared by presetting an air flow layer show a high specific capacity of 818.8 mA h g−1, an excellent cycling stability of 520 h, and a wide temperature‐adaptive from −40 to 60 °C. This work not only offers possibilities by improving metal‐loading and catalytic site utilization for exploring efficient SACs, but also provides strategies for device structure design toward advanced ZABs.

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Single-atom catalysis has become a new branch in heterogeneous catalysis. Although the naturally produced SiO2 -based materials are abundant and stable, fabrication of single-atom catalysts on such supports with high loading remains as a formidable challenge due to the lack of bonding sites to anchor the isolated metal species. Herein, modifying the diatomite, a kind of pure SiO2 mineral, with CeO2 nanoparticles is demonstrated to increase the defect sites on the support. The enhanced metal-support interaction maintains the atomic dispersion of Pt species with above 1 wt.% loading, exhibiting good performance in the selective hydrogenation of phenylacetylene to styrene.

Single atom catalyst (SAC) is one of the most efficient and versatile catalysts with well‐defined active sites. However, its facile and large‐scale preparation, the prerequisite of industrial applications, has been very challenging. This dilemma originates from the Gibbs–Thomson effect, which renders it rather difficult to achieve high single atom loading (< 3 mol%). Further, most synthesizing procedures are quite complex, resulting in significant mass loss and thus low yields. Herein, a novel metal coordination route is developed to address these issues simultaneously, which is realized owing to the rapid complexation between ligands (e.g., biuret) and metal ions in aqueous solutions and subsequent in situ polymerization of the formed complexes to yield SACs. The whole preparation process involves only one heating step operated in air without any special protecting atmospheres, showing general applicability for diverse transition metals. Take Cu SAC for an example, a record yield of up to 3.565 kg in one pot and an ultrahigh metal loading 16.03 mol% on carbon nitride (Cu/CN) are approached. The as‐prepared SACs are demonstrated to possess high activity, outstanding selectivity, and robust cyclicity for CO2 photoreduction to HCOOH. This research explores a robust route toward cost‐effective, massive production of SACs for potential industrial applications.

Abstract Lithium‐sulfur (Li‐S) batteries exhibit high energy density potential but suffer from lithium polysulfide (LPS) shuttling and sluggish conversion kinetics, hindering practical application. Here, a novel approach incorporating out‐of‐plane single‐atom catalysts (SACs) into a tetrathiocine‐linked porous organic polymer (POP) framework is introduced. This design enables precise spatial distribution of active metal sites, enhancing interactions with soluble LPSs. The out‐of‐plane configuration further supports unique coordination motifs, accelerating the transformation of soluble LPSs to solid phases and effectively mitigating the shuttle effect. The resultant Pt‐based SAC separator achieves outstanding catalytic efficiency, cycling stability, and capacity retention under high sulfur loading. The findings establish a foundational strategy that integrates advanced molecular design with electrochemical performance, offering a promising avenue for improving the practicality and efficiency of Li‐S battery technology.

Nonradical Fenton-like catalysis offers an opportunity to degrade extracellular antibiotic resistance genes (eARGs). However, high-loading single-atom catalysts (SACs) with controllable configurations are urgently required to selectively generate high-yield nonradicals. Herein, we constructed high-loading Fe SACs (5.4-34.2 wt %) with uniform Fe-N4 sites via an optimized coordination balance of supermolecular assembly for peroxymonosulfate activation. The selectivity of singlet oxygen (1O2) generation and its contribution to eARGs degradation were both >98%. This targeting strategy of oxidizing guanines with low ionization potentials by 1O2 allowed 7 log eARGs degradation within 10 min and eliminated their transformation within 2 min, outperforming most reported advanced oxidation processes. Relevant interactions between 1O2 and guanines were revealed at a single-molecule resolution. The high-loading Fe SACs exhibited excellent universality and stability for different eARGs and water matrices. These findings provide a promising route for constructing high-loading SACs for efficient and selective Fenton-like water treatment.

Renewable biomass serves as a cost-effective source of carbon matrix to carry single-atom catalysts (SACs). However, the natural abundant oxygen in these materials hinders the sufficient dispersion of element with high oxygen affinity such iron (Fe). The lowered-density and oxidized SACs greatly limits their catalytic applications. Here we develop a facile continuous activation (CA) approach for synthesizing robust biomass-derived Fe-SACs. Comparing to the traditional pyrolysis method, the CA approach significantly increases the Fe loading density from 1.13 atoms nm−2 to 4.70 atoms nm−2. Simultaneously, the CA approach induces a distinct coordination tuning from dominated Fe-O to Fe-N moieties. We observe a pH-universal oxygen reduction reaction (ORR) performance over the CA-derived Fe-SACs with a half-wave potential of 0.93 V and 0.78 V vs. RHE in alkaline and acidic electrolyte, respectively. Density functional theory calculations further reveal that the increased Fe-N coordination effectively reduces the energy barriers for the ORR, thus enhancing the catalytic activity. The Fe-SACs-based zinc-air batteries show a specific capacity of 792 mA·h·gZn−1 and ultra-long life span of over 650 h at 5 mA cm−2. Developing efficient single-atom catalysts for clean energy technologies is still challenging. Here, the authors report a facile method to increase the density and tune the coordination of iron atom loaded in single-atom catalysts that boosts the activity for pH-universal oxygen electrolysis.

The performance of single‐atom catalysts is greatly influenced by the chemical environment surrounding the central atom. Here, a salt‐assisted method is employed to transform the tetrahedral coordination structure of zeolitic imidazolate frameworks ‐ 8 (ZIF‐8) into a planar square coordination structure without altering the ligands. During the subsequent carbonization process, concurrent with the evaporation of zinc atoms, the structure of the nitrogen and carbon carriers (NC carriers) undergoes a transition from five‐membered rings to six‐membered rings to preserve the 2D structure. This transition results in the generation of additional defect sites on the 2D‐NC substrates. Hence, the Pt single‐atom catalysts with planar square coordination symmetries can be precisely prepared via electrodeposition (denoted as 2D‐Pt SAC). The Pt loading of 2D‐Pt SAC is 0.49 ± 0.03 µg cm−2, higher than that of 3D‐Pt SAC (0.37 ± 0.04 µg cm−2). In the context of the hydrogen oxidation reaction electrocatalysis, under an overpotential of 50 mV, these single‐atom catalysts with 2D coordination exhibit mass activities of 2396 A gPt−1 (32 times higher than commercial Pt/C catalyst, 2 times higher than 3D‐PtNC).

Significance Single-site-based catalysts exhibit high atom efficiency and tunable structure–activity properties. However, their real-world application remains tenuous as their activity is related to the low metal loading; otherwise, stability issues become relevant. We developed a scalable method for synthesizing thermally stable, high-loading single Cu site catalysts, which exhibit superior activity and selectivity in NH3 oxidation compared to nanoparticle-based catalysts. A unique reaction pathway was unambiguously demonstrated for the single Cu site catalyst through operando X-ray absorption fine structure and diffuse reflectance infrared Fourier transform spectroscopy, addressing the shortcomings in fundamental mechanistic steps, which have lagged behind empirical catalysts screening. This work marks an advancement in single-site catalysis and contributes to mechanistic understanding, fostering improvements in catalyst design.

Abstract Single‐atom catalysts (SACs) offer stable, well‐defined active sites by anchoring individual metal atoms on stable organic or inorganic supports, though achieving high metal loadings without clustering or leaching remains a major challenge. Here, we report a synthetic strategy for developing ultra‐high metal loading SACs based on palladium polyphthalocyanine covalent organic frameworks (COFs) synthesized via a mixed metal ionothermal approach, which involves the cyclization of tetracyanobenzene and tetracyanopyrazine as precursors in molten salt mixtures of PdCl2/ZnCl2 or PdCl2/ZnCl2/NaCl. This approach effectively combines the formation of crystalline polymeric hosts with metal impregnation in a single step, yielding COFs with atomically distributed Pd ions and metal contents of up to 22.2 wt%. Theoretical simulations reveal that the crystalline framework dynamically confines Pd atoms between different binding sites within the pores, preventing dimerization and ensuring long‐term catalyst stability. The synthesized catalysts were evaluated under continuous flow conditions, exhibiting stable performance with yields as high as 90% and maintaining stability over a 24 h time‐on‐stream under low‐conversion conditions. These results establish a new benchmark for SACs and underscore the importance of dynamic confinement approach in achieving high metal loadings on crystalline organic supports.

A nitrogen-coordinated Fe single-atom catalyst (SA Fe-N/C) is synthesized using a homogeneous ethanol-based dissolution system with bamboo kraft lignin serving as the carbon source. Uniformly dispersed Fe atoms with an interatomic distance of less than 2 Å throughout the SA Fe-N/C structure are revealed through X-ray absorption spectral analysis and HAADF-STEM images, which possessed a high Fe loading of 2.69%. The degradation rate of bisphenol A (BPA) approached 99% within 5 min, with the observed rate constant (kobs) of the catalysts markedly increasing from 0.070 to 0.615 min-1. The catalyst-mediated electron transfer pathway is identified as the predominant mechanism for BPA degradation. Both experimental data and DFT analysis of the nitrogen ligands demonstrated that pyridinic N-coordinated Fe single atoms are the principal active sites, attributed to the enhanced electron density and delocalization concentrated around the Fe sites. These findings significantly elucidate the role of nitrogen ligands in designing efficient lignin-derived carbon single-atom catalysts for environmental applications.

Ag single-atom catalysts (SACs) are promising for electrochemical CO2 reduction reaction (e-CO2RR) due to their high atom utilization and CO selectivity, yet they often suffer from agglomeration and instability. Here, we employ hydrogen-substituted graphdiyne (HGDY) as a robust support, where abundant alkyne groups strongly coordinate and stabilize atomically dispersed Ag sites. By systematically tuning Ag loading (0.3-10 wt.%), we achieve precise control over active sites and product distribution. The optimized Ag3.7-HGDY catalyst achieves a remarkable CO Faradaic efficiency (FECO) of 98.1% with a turnover frequency (TOF) of 26.5 s-1, maintaining a FECO of ≥97% across a wide potential window (-0.7 to -1.2 V vs RHE). Moreover, Ag loading enables dynamic modulation of CO/H2 ratios in syngas, highlighting the tunability of the system. This work demonstrates an effective strategy for anchoring noble metals via alkyne coordination, offering a generalizable pathway toward the rational design of stable and scalable single-atom catalysts for CO2 conversion.

Transition metal single atom catalysts (TM SACs) are the most promising oxygen reduction reaction (ORR) catalysts for proton exchange membrane fuel cells (PEMFCs) and metal-air batteries. However, the low density of M-Nx active sites seriously hinders further improvement of the ORR electrocatalytic activity. Here, a strategy for encapsulating nitrogen-rich guest molecules (triethylenediamine cobalt complex, [Co(en)3]3+) was proposed to construct a high-performance cobalt single-atom catalyst (Co-encapsulated SAC/NC). With this strategy, the guest molecules are encapsulated into metal-organic framework (MOF) cages as an additional cobalt source to boost cobalt loading, while abundant nitrogen from guest molecules contributes to the formation of Co-N4 active sites. Remarkably, the resulting Co-encapsulated SAC/NC has a high cobalt loading amount of 4.03 wt%, and spherical aberration-corrected transmission electron microscopy (AC-TEM) has confirmed that most cobalt exists in a single-atom state. As a result, the Co-encapsulated SAC/NC exhibits excellent ORR catalytic performance with a half-wave potential of 0.88 V. Furthermore, Zn-air batteries employing Co-encapsulated SAC/NC as air cathode show high peak power density and excellent cycling stability. Density functional theory (DFT) calculations reveal that adjacent active sites have different rate-determining steps and lower reaction energy barriers than a single active site.

Environmental photocatalysis is a promising technology for treating antibiotics in wastewater. In this study, a supercritical carbonization method was developed to synthesize a single-atom photocatalyst with a high loading of Ni (above 5 wt.%) anchored on a carbon-nitrogen-silicate substrate for the efficient photodegradation of a ubiquitous environmental contaminant of tetracycline (TC). The photocatalyst was prepared from an easily obtained metal-biopolymer-inorganic supramolecular hydrogel, followed by supercritical drying and carbonization treatment. The low-temperature (300°C) supercritical ethanol treatment prevents the excessive structural degradation of hydrogel and greatly reduces the metal clustering and aggregation, which contributed to the high Ni loading. Atomic characterizations confirmed that Ni was present at isolated sites and stabilized by Ni-N and Ni-O bonds in a Ni-(N/O)6C/SiC configuration. A 5% Ni-C-Si catalyst, which performed the best among the studied catalysts, exhibited a wide visible light response with a narrow bandgap of 1.45 eV that could efficiently and repeatedly catalyze the oxidation of TC with a conversion rate of almost 100% within 40 min. The reactive species trapping experiments and electron spin resonance (ESR) tests demonstrated that the h+, and ·O2- were mainly responsible for TC degradation. The TC degradation mechanism and possible reaction pathways were provided also. Overall, this study proposed a novel strategy to synthesize a high metal loading single-atom photocatalyst that can efficiently remove TC with high concentrations, and this strategy might be extended for synthesis of other carbon-based single-atom catalysts with valuable properties.

Metal-catalyzed semi-hydrogenation of alkynes is an important step in organic synthesis to produce diverse chemical compounds. However, conventional noble metal catalysts often suffer from poor selectivity owing to over-hydrogenation. Here, we demonstrate a high-loading bimetallic AgCu–C3N4 single-atom catalyst (SAC) for alkyne semi-hydrogenation. The AgCu–C3N4 SACs exhibit higher activity and selectivity (99%) than their low-loading variants due to the synergistic interaction of heteronuclear Ag–Cu sites at small inter-site distances. Using a combination of techniques such as phenylacetylene-DRIFTS, H2-temperature programmed desorption and DFT calculations, we showed that the cooperative bimetallic interaction during alkyne semi-hydrogenation was achieved by isolated Ag centers as hydrogen activation sites and isolated Cu centers as alkyne activation sites. Our work highlights the importance of achieving high catalyst loading to reduce the inter-site distance in bimetallic SACs for cooperative interactions, which can potentially open new catalytic pathways for synthesizing fine chemicals and pharmaceuticals.

Electrocatalytic denitrification (ECDN) for reduction of NO3 - to N2 is an effective and environmentally benign strategy for nitrogen-neutral cycle, but N2 selectivity is poor due to undesirable adsorption of nitrogen oxide intermediates and kinetic sluggishness of N-N coupling. In this study, triggering of p-d orbital hybridization is reported on high-density V-shaped atomically dispersed bimetallic electrocatalyst (CuSn-NC) with two Cu-N3 terminals and one Sn-N2 tip for stabilizing the key intermediates essential for N2-selective ECDN. Results reveal that ≈22.3 wt.% metal-loading bimetallic single-atom CuSn-NC electrocatalyst can achieve 94.1% NO3 - removal with N2 selectivity as high as 81.7%. A combination of operando measurements and theoretical calculations further verify the p-d orbital hybridization between p-block stannum (Sn) and d-block copper (Cu) in CuSn dual atom sites, which the resultant rate-determining step of *NO3 to *NO2 and selectivity-determining step of N-N coupling are accelerated by optimizing the binding of intermediates on Cu-N3 and Sn-N2 tip sites synergistically. This study provides the proof-of-concept demonstration of designing a bimetallic single-atom electrocatalyst for highly N2-selective ECDN, which offers a promising approach to nitrogen neutrality.

Atomically dispersed, non-noble-metal catalysts represent promising alternatives to costly platinum-group electrocatalysts, yet precise control over metal site proximity remains challenging. Herein, we report the synthesis of ultrathin (∼1.5 nm) N-doped carbon nanosheets decorated with densely packed single-atom copper sites (Cu SAs/N-CS), achieved via controlled pyrolysis of a Cu-1H-1,2,4-triazole complex precursor. The resulting Cu SAs/N-CS exhibits a high copper loading (3.17 wt %) with a remarkably short average interatomic distance (∼3.1 Å) between adjacent Cu atoms. Inspired by multicopper oxidase enzymes, these closely spaced Cu active sites facilitate efficient four-electron (4e-) oxygen reduction reactions (ORRs), displaying superior catalytic performance and long-term stability in both neutral and alkaline media. Specifically, Cu SAs/N-CS achieves impressive half-wave potentials of 0.68 V (neutral) and 0.91 V (alkaline) vs RHE, rivaling commercial Pt/C under neutral conditions and outperforming it in alkaline electrolytes. Density functional theory (DFT) analyses indicate that short-range Cu site proximity upshifts the d-band center, strengthens O2 adsorption, and significantly lowers the activation barrier for the 4e- ORR pathway, thus elucidating the mechanism behind its exceptional catalytic activity.

While electrocatalytic reduction of nitrate to ammonia presents a sustainable solution for addressing both the environmental and energy issues within the nitrogen cycle, it remains a great challenge to achieve high selectivity and activity due to undesired side reactions and sluggish reaction kinetics. Here, we fabricate a series of metal-N-C catalysts that feature hierarchically ordered porous structure and high-density atomically dispersed metals (HD M1/PNC). Specifically, the as-prepared HD Fe1/PNC catalyst achieves an ammonia production rate of 21.55 mol gcat-1 h-1 that is at least 1 order of magnitude enhancement compared with that of the reported metal-N-C catalysts, while maintaining a 92.5% Faradaic efficiency when run at 500 mA cm-2 for 300 h. In addition to abundant active sites, such high performance benefits from the fact that the high-density Fe can more significantly activate the adjacent N/C sites through charge redistribution for improved water adsorption/dissociation, providing sufficient active hydrogen to Fe sites for nitrate ammoniation, compared with the low-density counterpart. This finding deepens the understanding of high-density metal-N-C materials at the atomic scale and may further be used for designing other catalysts.

No abstract available

Highly active catalysts that can directly utilize renewable energy (e.g., solar energy) are desirable for CO2 value‐added processes. Herein, aiming at improving the efficiency of photodriven CO2 cycloaddition reactions, a catalyst composed of porous carbon nanosheets enriched with a high loading of atomically dispersed Al atoms (≈14.4 wt%, corresponding to an atomic percent of ≈7.3%) coordinated with N (AlN4 motif, Al–N–C catalyst) via a versatile molecule‐confined pyrolysis strategy is reported. The performance of the Al–N–C catalyst for catalytic CO2 cycloaddition under light irradiation (≈95% conversion, reaction rate = 3.52 mmol g−1 h−1) is significantly superior to that obtained under a thermal environment (≈57% conversion, reaction rate = 2.11 mmol g−1 h−1). Besides the efficient photothermal conversion induced by the carbon matrix, both experimental and theoretical analysis reveal that light irradiation favors the photogenerated electron transfer from the semiconductive Al–N–C catalyst to the epoxide reactant, facilitating the formation of a ring‐opened intermediate through the rate‐limiting step. This study not only provides an advanced Al–N–C catalyst for photodriven CO2 cycloaddition, but also furnishes new insight for the rational design of superior photocatalysts for diverse heterogeneous catalytic reactions in the future.

Room-temperature sodium-sulfur (Na-S) batteries are emerging as a promising next-generation energy storage technology, offering high energy densities at low cost and utilizing abundant elements. However, their practical application is hindered by the shuttle effect of sodium-polysulfides and the sluggish kinetics of sulfur redox reactions. In this study, we demonstrate a heteronuclear diatomic catalyst featuring Fe and Co bimetallic sites embedded in nitrogen-doped hollow carbon nanospheres (Fe-Co/NC) as an effective sulfur host at the cathode of Na-S batteries. Aberration-corrected high-angle annular dark field scanning transmission electron microscopy demonstrates the presence of isolated Fe-Co atomic pairs, while synchrotron radiation X-ray absorption fine structure analysis confirms the (Fe-Co-N6) coordination structure. Density functional theory calculations show that the introduction of Fe atoms induces electron delocalization in Co(II), shifting the electronic configuration from a low-spin to a higher-spin state. This shift enhances the hybridization of the Co dz2 orbitals with the antibonding π orbitals of sulfur atoms within the sodium sulfide species that accelerates their catalytic conversion. As a result, Fe-Co/NC-based cathodes exhibit excellent cycling stability (378 mAh g-1 after 2000 cycles) and impressive rate performance (341.1 mAh g-1 under 5 A g-1).

Na‐seawater batteries (SWBs) are environmentally friendly energy storage system that utilizes abundant seawater as an electrolyte alternative to conventional distilled water‐based and organic electrolytes. To achieve high energy efficiency in Na‐SWBs, it is necessary to enhance the activity of bifunctional oxygen electrocatalysts. In this study, an atomically dispersed iron and cobalt dual‐atom nitrogen‐doped lens‐shaped mesoporous carbon (FeCo‐LMC) particles is synthesized as a SWB cathode material using the spinodal decomposition of the polymer blend and selective precursor positioning. The well‐aligned mesoporous structure and synergetic effect of the dual‐atom site realize FeCo‐LMC as a comparable bifunctional oxygen catalyst with the lowest overpotential difference (EOER−EORR) among the other catalysts with natural seawater electrolyte. When applied to the SWB system, the FeCo‐LMC shows a highly improved charge/discharge performance compared to Pt/C and a stable cycling performance for 200 h. Density functional theory calculations reveal the enhanced oxygen catalytic activity of FeCo‐LMC owing to electron delocalization and d‐band center adjustment of FeN4–CoN4 structure.

Enlarging the M-Nx active-site density is an effective route to enhance the ORR performance of M-N-C catalysts. In this work, a single-atom catalyst Cu–N@Cu–N–C with enlarged Cu–N4 active site density was prepared by the second doping and pyrolysis (SDP) of Cu–N–C derived from Cu-doped zeolite imidazole frameworks. The half-wave potentials of Cu–N@Cu–N–C were measured as 0.85 V in alkaline electrolyte and 0.75 V in acidic media, which was 50 mV and 60 mV higher than that of Cu–N–C, respectively. N2 adsorption–desorption isotherm curves and corresponding pore distribution analysis were used to verify the successful filling of additional Cu and N in micropores of Cu–N–C after SDP. The obvious increase in Cu contents for Cu–N@Cu–N–C (1.92 wt%) compared with Cu–N–C (0.88 wt%) tested by ICP demonstrated the successful doping of Cu into Cu–N–C. XAFS analysis confirmed the presence of Cu–N4 single-atom active centers in Cu–N@Cu–N–C. The N 1 s high-resolution XPS results proved a great increase in Cu–N4 contents from 13.15% for Cu–N–C to 18.36% for Cu–N@Cu–N–C. The enhanced ORR performance of Cu–N@Cu–N–C was attributed to the enlargement of Cu–N4 active site density, providing an effective route for the preparation of efficient and low-cost ORR catalysts.

Hydroxide exchange membrane fuel cells (HEMFCs) have the advantages of using cost-effective materials, but hindered by the sluggish anodic hydrogen oxidation reaction (HOR) kinetics. Here, we report an atomically dispersed Ir on Mo2C nanoparticles supported on carbon (IrSA-Mo2C/C) as highly active and stable HOR catalysts. The specific exchange current density of IrSA-Mo2C/C is 4.1 mA cm−2ECSA, which is 10 times that of Ir/C. Negligible decay is observed after 30,000-cycle accelerated stability test. Theoretical calculations suggest the high HOR activity is attributed to the unique Mo2C substrate, which makes the Ir sites with optimized H binding and also provides enhanced OH binding sites. By using a low loading (0.05 mgIr cm−2) of IrSA-Mo2C/C as anode, the fabricated HEMFC can deliver a high peak power density of 1.64 W cm−2. This work illustrates that atomically dispersed precious metal on carbides may be a promising strategy for high performance HEMFCs. High-performance hydroxide exchange membrane fuel cells rely on the anode loading of platinum-group metals. Here, the authors report a highly active hydrogen oxidation electrocatalyst which contains atomically dispersed Ir on Mo2C nanoparticles supported on a carbon substrate.

The catalytic partial oxidation of methane (POM) presents a promising technology for synthesizing syngas. However, it faces severe over-oxidation over catalyst surface. Attempts to modify metal surfaces by incorporating a secondary metal towards C–H bond activation of CH4 with moderate O* adsorption have remained the subject of intense research yet challenging. Herein, we report that high catalytic performance for POM can be achieved by the regulation of O* occupation in the atomically dispersed (AD) MoNi alloy, with over 95% CH4 conversion and 97% syngas selectivity at 800 °C. The combination of ex-situ/in-situ characterizations, kinetic analysis and DFT (density functional theory) calculations reveal that Mo-Ni dual sites in AD MoNi alloy afford the declined O2 poisoning on Ni sites with rarely weaken CH4 activation for partial oxidation pathway following the combustion reforming reaction (CRR) mechanism. These results underscore the effectiveness of CH4 turnovers by the design of atomically dispersed alloys with tunable O* adsorption. The catalytic partial oxidation of methane (POM) is a promising technology for synthesizing syngas but suffers from severe over-oxidation on the catalyst surface. Here the authors demonstrate that regulating O* occupation in an atomically dispersed MoNi alloy can achieve high catalytic performance for POM.

Single‐atom catalysts (SACs) present a promising subclass of classic heterogeneous catalysts by maximizing metal dispersion and enhancing efficiency. Although high‐density SACs (HD‐SACs) are reported, their synthesis is typically constrained to specific metal‐support combinations and high‐temperature annealing, limiting their translation to wider applications. Herein, a universal bottom‐up approach for the preparation of mono‐ and bimetallic HD‐SACs based on the polycondensation of 1,2,4,5‐benzenetetramine with a wide range of metal monomers containing 1,10‐phenanthroline‐5,6‐dione ligands is introduced. The synthesized materials are atomically dispersed and exhibit metal loadings up to 27.5 wt% with high structural stability. Their versatility as catalysts is explored in electrocatalytic and photocatalytic applications. The materials exhibit remarkable stability under operational conditions. Furthermore, this synthetic strategy is scaled up and automated, demonstrating the robustness and reproducibility and laying the groundwork for self‐optimizing data‐driven materials discovery.

Visible light driven carbon dioxide (CO2) reduction to ethylene (C2H4) is a promising pathway to obtain renewable fuels and valuable chemicals. However, the insufficient supply of *CO/CO severely limits the rate of C-C coupling toward C2H4. Herein, we present a synergistic engineering strategy to construct a Fe0.2/H-MOF-1 composite catalyst by anchoring high-density iron single atoms sites (Fe SAs) onto a pyridinic nitrogen rich metal-organic framework (H-MOF-1). Under visible light, the catalyst achieves an exceptional C2H4 yield of 1056.2 µmol·g-1·h-1. This performance surpasses state-of-the-art systems for visible light driven CO2-to-C2H4. The X-ray absorption fine structure (XAFS) analysis, CO adsorption experiments and density functional theory (DFT) calculations demonstrate that the Fe-N active sites in the Fe0.2/H-MOF-1 catalyst not only significantly reduce the energy barrier from *COOH to *CO but also maintain abundant *CO/CO for C-C coupling through strong CO adsorption, thus efficiently promoting the rapid generation of C2H4. This study provides insights into the rapid generation of C2H4 through photocatalytic CO2 reduction, paving the way for visible light-driven CO2 reduction reactions.

The metal-nitrogen-carbon (M-N-C)-based catalysts are promising to replace PGM (platinum group metal) to accelerate oxygen reduction reaction due to their excellent electrocatalytic performance. However, the inferior intrinsic activity and poor active site density confining further improvement in their performance. Modulating the electronic structure and reasonably designing the pore structure are widely acknowledged effective strategies to boost the activity of the M-N-C catalysts. However, it is a great challenge to form abundant pores to regulate the electronic structure via the facile method. Herein, a hierarchical, porous dual-atom catalyst FeNi-NPC-1000 has been architectured by the Na2CO3 template method and bimetallic doping modification strategy. Benefitting from the optimized pore and electronic structure, the as-prepared FeNi-NPC-1000 possesses a high specific surface area (1412.8 m2 g-1) and improved ORR activity (E1/2 = 0.877 V vs RHE), which is superior to that of Pt/C (E1/2 = 0.867 V vs RHE). With the evidence of AC-STEM, XAS, and DFT, the FeNi-N8-C moiety is proven to be the key active site to realize high-efficiency ORR catalysis. When assembled it as an air cathode of ZABs, FeNi-NPC-1000 displays superior discharge performance (Pmax = 367.1 mW cm-2) and a stable battery long-life. This article will provide a new strategy for designing dual-metal atomic catalysts applied in metal-air batteries.

Electrochemical carbon dioxide reduction reaction (CO2RR) is one of the most prospective strategies to achieve carbon neutrality. Multi‐carbon compound (C2+) products have higher commercial value and wider applications, among which ethanol is a widely used chemical feedstock and high energy density fuel. Here, we prepared nitrogen‐doped carbon nanofibers containing copper‐zinc double atoms using the electrospinning technique and controlled the content of both metal atoms by varying the calcination temperature. This catalyst exhibited ultra‐high selectivity for ethanol at low potentials. Ethanol selectivity at −0.3 V versus RHE was more than 60% with the total alcohol selectivity of over 80%. Meanwhile, we explored the ethanol production pathway by combining density‐functional theory (DFT) and ATR‐FTIR spectroscopy, and found that OCCO* intermediates were most abundant for the optimal ratio of Cu to Zn atoms, lowering the energetic barriers to ethanol formation, and thus improving the selectivity of ethanol production.

ABSTRACT Synthesis of atomically dispersed catalysts with high metal loading and thermal stability is challenging but particularly valuable for industrial application in heterogeneous catalysis. Here, we report a facile synthesis of a thermally stable atomically dispersed Ir/α-MoC catalyst with metal loading as high as 4 wt%, an unusually high value for carbide supported metal catalysts. The strong interaction between Ir and the α-MoC substrate enables high dispersion of Ir on the α-MoC surface, and modulates the electronic structure of the supported Ir species. Using quinoline hydrogenation as a model reaction, we demonstrate that this atomically dispersed Ir/α-MoC catalyst exhibits remarkable reactivity, selectivity and stability, for which the presence of high-density isolated Ir atoms is the key to achieving high metal-normalized activity and mass-specific activity. We also show that the water-promoted quinoline hydrogenation mechanism is preferred over the Ir/α-MoC, and contributes to high selectivity towards 1,2,3,4-tetrahydroquinoline. The present work demonstrates a new strategy in constructing a high-loading atomically dispersed catalyst for the hydrogenation reaction.

Electrosynthesis of acetate from carbon monoxide (CO) powered by renewable electricity offers one promising avenue to obtain valuable carbon-based products but undergoes unsatisfied selectivity because of the competing hydrogen evolution reaction. We report here a cerium single atoms (Ce-SAs) modified crystalline-amorphous dual-phase copper (Cu) catalyst, in which Ce SAs reduce the electron density of the dual-phase Cu, lowering the proportion of interfacial K+ ion hydrated water (K·H2O) and thereby decreasing the H* coverage on the catalyst surface. Meanwhile, the electron transfer from dual-phase Cu to Ce SAs yields Cu+ species, which boost the formation of active atop-adsorbed *CO (COatop), improving COatop-COatop coupling kinetics. These together lead to the preferential pathway of ketene intermediate (*CH2-C=O) formation, which then reacts with OH- enriched by pulsed electrolysis to generate acetate. Using this catalyst, we achieve a high Faradaic efficiency of 71.3 ± 2.1% toward acetate and a time-averaged acetate current density of 110.6 ± 2.0 mA cm−2 under a pulsed electrolysis mode. Furthermore, a flow-cell reactor assembled by this catalyst can produce acetate steadily for at least 138 hours with selectivity greater than 60%. Electrosynthesis of acetate from CO using renewable electricity faces low selectivity. Here, the authors report a cerium single atom modulated copper catalyst, where cerium atoms tailor the interfacial water structure, enabling highly selective CO-to-acetate conversion under pulsed electrolysis.

Rechargeable zinc-air batteries (ZABs) face significant challenges in achieving both high power density and long-term stability, primarily due to limitations in catalytic materials for oxygen electrodes. Here, we present a trimetal planar heterogeneous metal catalyst featuring atomically dispersed ZnN4, FeN4, and CoN4 sites supported on a porous nitrogen-doped carbon substrate (ZnFeCo-NC) through a templating approach. By fine-tuning the content of each metal, the optimized ZnFeCo-NC-based ZAB achieves a high peak power density of 244 mW cm-2 and maintains durable performance for 500 h at 10 mA cm-2. Ab initio molecular dynamics simulations reveal that the ZnFeCo-NC catalyst configuration remains stable at 300 K during the oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) process. Further theoretical calculations demonstrate that the introduction of adsorbed OH groups effectively tunes the electronic structure redistribution of metal active sites, particularly improving the catalytic performance at the Fe site for ORR and the Co site for the OER. These findings provide insights into the rational design of high-performance electrocatalysts in energy storage technologies.

Single‐atom nanozymes (SAzymes) can maximize atomic utilization efficiency and construct highly active catalytic sites for biomedical applications. Herein, atomically dispersed iron (Fe) and cobalt (Co) dual sites anchored N‐doped graphene carbon (FeCoCN) catalyst is rationally constructed to achieve photothermally augmented catalytic oxidation for effective biocatalytic tumor nanotherapy. Compared with Fe SAzyme, FeCoCN SAzyme can significantly accelerate the charge transfer and improve the activity of catalytic reactions. Co‐doping optimizes coordination structure and charge redistribution by facilitating the ratio of Fe2+ and regulating charge transfer between different metal sites and nearby coordination atoms. Bimetallic FeCoCN SAzyme possessed an ultra‐high affinity for substrate H2O2, and the catalytic kinetic Km value (0.589 mm) is superior to natural catalase and most reported nanozymes. The boosted catalytic activity in producing •OH is identified by density functional theory (DFT) studies. In vivo, investigation demonstrates that atomically dispersed Fe and Co dual sites anchored FeCoCN SAzyme significantly suppresses tumor proliferation under NIR laser irradiation by photothermally enhanced catalytic oxidation. Additionally, Fe‐ and Co‐doping in FeCoCN make it suitable as a tracer for T2 magnetic resonance imaging. This work provides a paradigm to rationally design bimetallic SAzymes with enhanced biocatalytic performance for tumor treatment.

Zinc-air batteries (ZABs) have garnered significant interest due to their environmental friendliness, low cost, and high energy density. However, their practical application is significantly hindered by high overpotential and sluggish reaction kinetics. Here, we propose a hollow nitrogen-doped carbon supported atomically dispersed Fe and Mn sites (FeMn-HNC) through a facile NaCl-assisted pyrolysis strategy. The synthesized FeMn-HNC catalyst possesses a hollow porous structure, resulting in exceptional oxygen reduction reaction (ORR) catalytic activity, remarkable durable stability, and good tolerance to methanol. Furthermore, integrating this catalyst into ZABs demonstrates significant performance advantages, achieving a maximum power density of 223.1 mW cm-2 and a high specific capacity of 804.3 mAh g-1. This study offers a promising approach for boosting the power density and specific capacity of nitrogen-doped carbon catalysts in ZABs.

The high overpotential and unsatisfactory stability of RuO2-based catalysts seriously hinder their application in acidic oxygen evolution reaction (OER). Herein, a Ru@RuO2 core/shell catalyst doped with atomically dispersed Mn species, denoted as Ru@Mn-RuO2, is reported, which is prepared by a facile one-pot method. Detailed structural characterizations confirm that Mn is homogeneously and atomically distributed in RuO2 shell, which causes lattice contraction of RuO2. The as-prepared Ru@Mn-RuO2 exhibits a very low overpotential of 190 mV at the current density of 10 mA cm-2 and an excellent stability of 360 h, far surpassing the control samples Ru@RuO2 without atomically dispersed Mn dopants and home-made RuO2 nanoparticles without metallic Ru core. With the further assistance of density functional theory calculations, the enhanced OER activity of Ru@Mn-RuO2 is attributed to multiple synergistic effects, including the MnOx-Ru (oxide shell) synergy, MnOx-Ru (metal core) synergy, and the Ru (core)-RuO2 (shell) synergy. Besides, the atomically dispersed Mn doping can increase the formation energy of soluble Ru cations, thus leading to the excellent stability of the Ru@Mn-RuO2 catalyst. This work shines light on the design of electrocatalysts with multiple synergistic effects towards efficient acid water splitting.

Developing a high-performance membrane electrode assembly (MEA) poses a formidable challenge for fuel cells, which lies in achieving both high metal loading and efficient catalytic activity concurrently for MEA catalysts. Here, we introduce a porous Co@NC carrier to synthesize sub-4 nm PtCo intermetallic nanocrystals, achieving an impressive Pt loading of 27 wt %. The PtCo-CoNC catalyst demonstrates exceptional catalytic activity and remarkable stability for the oxygen reduction reaction. Advanced characterization techniques and theoretical calculations emphasize the synergistic effect between PtCo alloys and single Co atoms, which enhances the desorption of the OH* intermediate. Furthermore, the PtCo-CoNC-based cathode delivers a high power density of 1.22 W cm-2 in the MEA test owing to the enhanced mass transport, which is verified by the simulation results of the O2 distributions and current density inside the catalyst layer. This study lays the groundwork for the design of efficient catalysts with practical applications in fuel cells.

Single atom Fe catalysts coordinated with five N atoms (Fe-N 5 ) have been adopted for excellent CO 2 -to-CO conversion. However, Fe-N 5 catalysts typically face trade-offs among Faradaic efficiency ( FE ), current density, and stability, posing challenges for further commercialization. Additionally, the role of coordinated N species in their catalytic activities remains unclear. Herein, Fe-N 5 catalysts coordinated with a high abundance of pyridinic-N (Fe-N 5-pyri ) or pyrrolic-N (Fe-N 5-pyrro ) are synthesized. Both operando experiment results and theoretical calculation manifest that pyrrolic-N increases CO 2 adsorption capacity, reduces the reaction free energies required for CO 2 activation, and facilitates *CO desorption by weakening the bonding strength with reaction centers. As a result, Fe-N 5-pyrro exhibits superior CO 2 -to-CO conversion performance, achieving a maximum FE CO of 96.6 % and a partial current density exceeding – 130 mA cm — 2 in 0.5 M KHCO 3 , maintaining stable operation for over 100 h. This work highlights the role of nitrogen species in Fe-N 5 catalysts and provides a promising strategy for synthesizing robust catalyst for CO 2 electrochemical reduction.

Iron, one of the most abundant elements on earth and an essential element for living organisms, plays a crucial role in our daily metabolism. In the field of catalysis, the development of high-performance catalysts based on less toxic iron element is also of significant importance for green chemistry and a sustainable future. To construct Fe-based heterogeneous catalysts with excellent hydrogenation performance, precise modulation of the atomic coordination structure is a key strategy for enhancing catalytic activity. In this study, we present an in-situ coating method for applying a zeolitic imidazolate framework (ZIF) onto the surface of fungal hyphae. The asymmetric coordination structure of Fe1-N3P1 was precisely tailored by utilizing the phosphorus source from the fungus and the nitrogen source in the ZIFs. Detailed characterizations and density functional theory calculations revealed that the incorporation of ZIFs not only increased the specific surface area of catalysts, but also facilitated the dispersion of Fe2P nanoparticles into the Fe1-N3P1 center, making the lowest reaction energy barrier and resulting in the best performance for nitrobenzene hydrogenation when compared to the Fe2P nanoparticles and clusters. This research introduces a novel design concept for constructing asymmetric monoatomic configuration based on the inherent characteristics of natural microorganisms and the exogenous porous coordination polymers.

Water electrolysis is an eco-friendly technology that does not emit pollutants when connected to renewable energy and can obtain high purity hydrogen (>99.9%) through the process of electrochemically splitting water molecules into hydrogen and oxygen. Among them, proton exchange membrane water electrolysis (PEMWE) has the advantage of high current density, low gas crossover, high gas purity, and high pressure operation compared to existing alkaline water electrolysis.[1] The material that shows the best catalytic activity in the hydrogen evolution reaction (HER) is platinum (Pt), which has a low overpotential and high exchange current density. Therefore, it has been the subject of various studies in the fields of catalysis and electrochemistry to investigate the effect of the size and structure of Pt nanoparticles and nanostructures on electrocatalytic activity.[2,3] However, due to the limited resources and high cost of platinum, the use of platinum acts as an obstacle to commercialization of PEMWE. Accordingly, many studies have been conducted on the development of low-platinum hydrogen generation catalysts to reduce platinum usage and increase activity. has been in progress. In this study, a porous transport electrode incorporating a Ni catalyst in which Ru was atomically dispersed was fabricated through simple electrodeposition. The Ni98.1Ru1.9 catalyst doped with trace amounts of Ru showed a low overpotential of 35 mV at –10 mA cm-2 for hydrogen evolution and a low Tafel slope of 31 mV with excellent stability. It was found that optimized hydrogen adsorption strength and improved mobility of hydrogen adsorbates on the catalyst surface contributed to high performance through density functional theory calculations. As a result of further verifying the performance and durability by applying Ni98.1Ru1.9 to the hydrogen electrode of the PEMWE cell, it showed excellent performance of 6.0 A cm-2 at 2.25Vcell and high stability operating at 1 A cm-2 for 50 hours.[4] [References] [1] M. F. Kaya, N. Demir., Fuel Cells, 17 (2017) 37–47 [2] J. Solla-Gullón, R. Gómez, A. Aldaz, J.M. Pérezet., Electrochemistry Communications, 10 (2008) 319–322 [3] Maryam Bayati, Jose M. Abad, Craig A. Bridges, Matthew J. Rosseinsky, David J. Schiffrin, Journal of Electroanalytical Chemistry, 623 (2008) 19–28 [4] K-R. Yeo, H. Kim, K-S Lee, S. Kim, J. Lee, H. Park, S-K Kim, Applied Catalysis B: Environment and Energy, 346 (2024), 123738

Crystalline zeolites have been proven to be excellent supports for confining subnanometric metal catalysts to boost the propane dehydrogenation (PDH) reaction. However, the introduced metallic species may suffer from severe sintering and limited stability during the catalytic process, especially when utilizing an industrial impregnation method for metal incorporation. In this study, we developed a new type of support based on amorphous protozeolite (PZ), taking advantage of its adjustable silanol chemistry and zeolitic microporous characteristic for stabilizing atomically dispersed PtSn catalyst via a simple, cost-effective coimpregnation process. The combination of X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, in situ diffuse reflectance infrared Fourier transform spectroscopy under CO atmosphere, and density functional theory calculations confirmed the formation of highly dispersed active Ptδ+-Ox-Sn species in PtSn/PZ. The PtSn/PZ catalyst exhibited a high propane conversion of 45.4% and a high propylene selectivity of 99% (WHSV= 3.6 h-1, 550 °C), with a high apparent rate coefficient of 565 molC3H6·gPt-1·h-1·bar-1 at a high WHSV of 108 h-1, presenting a top-level performance among the state-of-the-art Pt-based catalysts prepared by in situ synthesis and impregnation methods. The silanol density determined the chemical state of PtSn species, showing a change from atomically dispersed Ptδ+-Ox-Sn sites to PtSn alloy with decreasing silanol density of supports. This work provides a general strategy using silanol-rich amorphous protozeolite as support for stabilizing various metal catalysts by the simple impregnation method and also offers an effective way for fine tailoring the chemical state of metallic species via a silanol-engineered approach.

Carbon-based, non-noble metal catalysts for the oxygen reduction reaction (ORR) are crucial for the large-scale application of metal-air batteries and fuel cells. Density functional theory calculations were performed to explore the potential of atomically dispersed MN4/C (M = Fe or Mn) as an ORR catalyst in an acidic electrolyte and the ORR mechanism on MN4/C was systematically studied. The results indicated MN4 as the active site of MN4/C and a four-electron OOH transformation pathway as the preferred ORR mechanism on the MN4/C surface. The Gibbs free energy diagram showed that the rate-determining step of the FeN4/C and MnN4/C catalysts is the formation of the second H2O molecule and OOH*, respectively. FeN4/C exhibited higher thermodynamic limiting potential (0.79 V) and, thus, higher ORR activity than MnN4/C (0.52 V) in an acidic environment; its excellent catalytic performance is due to the nice electron structure and adsorption properties of the FeN4 site. Therefore, this work demonstrates that atomically dispersed MN4/C is a promising catalyst for the ORR.

Lithium–sulfur (Li–S) batteries have attracted wide attention as high‐energy‐density energy storage devices, but their practical applications are hindered by the severe shuttle effect and sluggish kinetics of lithium polysulfides (LiPSs). To address these challenges, polar mediators are employed to chemisorb and catalyze LiPSs, but most of them suffer from low electronic conductivity and poor catalytic activity. Here, a novel strategy is reported to enhance both properties by dispersing Fe(III) atoms in VO2 nanoribbons(Fe‐VO2), creating electronic metal‐support interactions (EMSI) that modulate the electronic structure and charge transfer of VO2. Theoretical calculations reveal that EMSI lowers the energy barrier for the decomposition of Li2S from 1.60 to 1.32 eV and increases the electronic conductivity of VO2. Fe doping reduces the Li‐ions diffusion barrier from 1.42 eV in VO2 to 0.99 eV in Fe‐VO2. The Fe‐VO2 catalyst shows strong adsorption and fast converstion of LiPSs, resulting in high energy density and long cycling life of Li‐S batteries. The cathode with Fe‐VO2 maintains a higher capacity retention of 67% after 500 cycles at 1 C, compared with 52.4% and 53.6% for the carbon black based cathode and VO2 based cathode, respectively. This work demonstrates the potential of EMSI for designing efficient catalysts for Li–S batteries and provides new insights into the electronic structure engineering of polar mediators.

Simultaneously achieving high activity for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is the key to constructing rechargeable Zn-air batteries (ZABs). Here the complexation of 1,10-phenanthroline and the spatial confinement effect of closo-[B12 H12 ]2- are used to solidify metal-boron-cluster-organic-polymers on the surface of SiO2 microspheres to construct a bifunctional oxygen electrocatalyst (FeBCN/NHCS). Driven by FeBCN/NHCS, the half-wave-potential of ORR surpasses that of the Pt/C catalyst, reaching 0.893 V versus RHE, and the overpotential (η10 ) of OER is as low as 361 mV. The ZABs of FeBCN/NHCS as an air cathode not only have high power density and specific capacity, but also have charge-discharge durability. The FeBCN/NHCS is not only related to the high specific surface area, but also the high exposure rate of single-atom Fe and the doping of heteroatom B. This study provides an efficient oxygen electrocatalyst and also contributes wisdom to the acquisition of highly active oxygen electrocatalyst.

The predominant product of CO electroreduction (COER) is often acetate, with the Faradaic efficiency (FE) for ethanol usually falling below 50%. Herein, we propose a unique strategy to enhance product selectivity in COER, shifting it from acetate predominance toward ethanol generation via alloying atomic manganese (Mn) atoms with a face-centered cubic (FCC) copper (Cu) catalyst. By optimizing the atomic ratio of Mn to Cu, we observe an impressive enhancement of 8.8-fold for the ethanol-to-acetate FE ratio in the optimal Mn3Cu97 alloy compared to unalloyed FCC-phase Cu. Mn3Cu97 demonstrates a remarkable ethanol FE of nearly 70% at a high current density of 600 mA cm-2 in a membrane electrode assembly electrolyzer. Further theoretical analysis reveals that atomically dispersed Mn atoms generate synergistic active sites and modulate the adsorption strength of critical intermediates relevant to ethanol synthesis, thereby facilitating the transition from the acetate pathway to the ethanol pathway.

Efficient electrochemical nitrogen reduction reaction (NRR) under mild conditions is highly desired for achieving cost-effective application but is challenging to realize in practice. Previous studies have shown that atomically dispersed Mo on a graphene-like two-dimensional (2D) support can be a promising catalyst for NRR. Here, we show the outstanding electrocatalytic performance of a Mo-based atomically dispersed metal catalyst (ADMC) on a N-doped defective graphene support (Mox-N6-gra (x = 1-3)) by using density functional theory computations. Particular attention is paid to the underlying reaction mechanism for NRR. The computed formation energy and ab initio molecular dynamics simulation suggest that the N atoms doped on the graphene support can firmly anchor the Mo atoms in both Mo1-N6-gra and Mo2-N6-gra configurations, which are highly beneficial for NRR. In particular, Mo1-N6-gra exhibits high catalytic activity toward NRR via the distal mechanism with a limiting potential of -0.23 V, even higher than that of many ADMCs with a graphene-like support. Importantly, Mo1-N6-gra enables effective suppression of the competing hydrogen evolution reaction (HER). Additionally, Mo2-N6-gra is another high-performance ADMC for NRR with a limiting potential of -0.35 V and different catalytic mechanisms (i.e., the split-alternating and split-mixed mechanism). This computational study suggests two highly efficient ADMCs for N2 fixation, notably more efficient than previously reported ADMCs, and provides a design strategy for seeking a more optimal ADMC/support combination.

A key challenge in heterogeneous catalysis is to design atomically dispersed catalysts with high surface density, while simultaneously preventing agglomeration and promoting electronic metal-support interaction. Transition metal dichalcogenides (TMDs), such as platinum diselenide (PtSe2), offer a promising solution due to their unique structural and electronic properties. This study proposes a catalyst design that utilizes atomically dispersed transition metal species within the topmost layer of TMD as catalytic reaction sites. The substantial presence of surface-exposed Pt species on PtSe2 and their role as catalytic reaction sites are elucidated using operando ambient-pressure X-ray photoelectron spectroscopy. Moreover, significantly high O2 coverage on PtSe2, achieved by mitigating the exclusive adsorption of carbon monoxide (CO), leads to enhanced CO oxidation performance. The characteristic d-band structure and resulting high O2 coverage of PtSe2 are further confirmed with density functional theory calculations. Overall, this study highlights the potential of densely distributed atomic transition metal on TMDs, which allows electronic metal-chalcogen interactions and diverse reaction mechanisms. A major challenge in heterogeneous catalysis is creating atomically dispersed catalysts with high surface density that resist agglomeration and enhance metal-support interactions. Here, the authors propose a design using atomically dispersed transition metal species in the top layer of transition metal dichalcogenides as active sites.

CO2 electroreduction (eCO2R) holds promise as an environmentally friendly approach to reducing greenhouse gas emissions. Cu is a representative catalyst with high eCO2R activity. However, its selectivity for CH4 synthesis is still insufficient due to the slow eight-electron transfer to a single carbon, the predominance of C-C coupling reactions toward C2+ products on Cu, as well as occurrence of the hydrogen evolution reaction. Here, for high CH4 selectivity, we demonstrate a genuine hydrogen supply to atomically dispersed Cu sites (AD-Cu) via the cooperative function of oxygen vacancy (VO) formed on defective black anatase TiO2 (Cu-TiO2-H2), that is prepared by exposing Cu-doped TiO2 (Cu-TiO2) to hydrogen gas. Cu-TiO2-H2 exhibited a remarkable Faradaic efficiency for CH4 production of 63% and a partial current density of -120 mA cm-2. The catalytic mechanism for the high CH4 selectivity was elucidated using a variety of spectroscopies, such as electron spin resonance, reversed double-beam photoacoustic spectroscopy (RDB-PAS) and in situ Raman measurements, with the support of quantum chemical calculations. In situ Raman measurements revealed that Cu-TiO2-H2 greatly accelerates proton consumption for the hydrogenation of *CO intermediates and that the surface pH on Cu-TiO2-H2 is sufficiently high to stabilize *CHO intermediates, key species for CH4 formation. DFT calculations support the stability of the intermediates during the process of forming *CHO. All our results suggest that VO contiguous to AD-Cu on Cu-TiO2-H2 promotes water dissociation and smoothly supplies hydrogen to AD-Cu on Cu-TiO2-H2, thus facilitating CH4 formation in eCO2R.

Developing nonprecious metal oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalysts with both high activity and stability remains a critical challenge for advanced metal–air battery. In this work, we develop a ball‐milling assisted pyrolysis strategy to fabricate atomically dispersed Fe anchored on nitrogen‐doped graphene (Fe–N–C/Gra), which precisely constructs Fe‐Nx active centers for efficient ORR/OER bifunctional catalysis. The fabricated Fe–N–C/Gra‐600 demonstrates ORR half‐wave potential of 0.862 V and OER overpotential of 1.743 V at 10 mA cm−2, surpassing commercial Pt/C benchmarks. Remarkably, under high electrolyte concentration conditions, catalyst exhibits reduced OER overpotentials due to increased electrochemical active surface area and optimized electron transfer resistance. Noteworthy, the Zn–air battery equipped with Fe–N–C/Gra‐600 as air electrode catalyst, delivers a remarkable peak power density of 430 mW cm−2, along with excellent charge–discharge cycling stability at 10 mA cm−2. The outstanding bifunctional performance originates from synergistic effects of Fe–N–C/Gra‐600, in which atomically dispersed Fe accelerates adsorption and activation of reactants due to formation of Fe–Nx species, synergistically with high conductive property of graphene substrate. This study not only demonstrates great potential of graphene‐supported Fe–N–C single‐atom catalysts for metal–air battery applications but also provides a new strategy for preparing high‐performance nonprecious metal electrocatalysts.

Commercial V-W/TiO2 catalysts are extensively applied for NOx emission control in coal-fired power plants. However, their limited operating temperature range and low active site utilisation significantly restrict NOx removal efficiency, particularly during boiler load fluctuations. This study introduces atomically dispersed Ce-V/TiO2 catalysts synthesised using a dual-site coordination strategy, enhancing active site dispersion. This method addresses the limitations of low active site turnover frequency (TOF) and high energy barriers in rate-determining steps, resulting in an extended operating temperature range and improved NOx removal efficiency. Under identical conditions, Ce-V/TiO2 achieved 90 % NOx conversion from 290 to 450 °C, a substantial increase over the commercial catalyst (365-425 °C). Additionally, Ce-V/TiO2 exhibited a TOF of 3.58 × 10-3 s-1, 1.52 times higher than the commercial catalyst. Density functional theory (DFT) analysis demonstrated that CeV synergy accelerates the Eley-Rideal rate-determining step by lowering the activation energy for NH3 dissociation into -NH2, and reduces the energy barrier for -NHNO intermediate formation in the Langmuir-Hinshelwood pathway. This work overcomes poor low-temperature activity by leveraging CeV synergy, offering a strategy for efficient NOx removal across a broad temperature range with selective catalytic reduction catalysts.

The electrochemical carbon dioxide reduction reaction (CO 2 RR) represents a promising strategy for converting CO 2 into CO. Atomically dispersed transition metal sites have an exceptional ability to activate CO 2 . However, the strong hybridization between the 3 d orbitals of these transition metals and the 5σ or 2π * orbital of CO significantly impedes * CO desorption, thereby limiting the overall CO generation activity. In contrast, s ‐block metals, with diffuse 3 s electron clouds, exhibit weaker interactions with * CO. Nevertheless, their practical application is hindered by the high energy barrier associated with the formation of the * COOH intermediate. To address these challenges, a fluorine(F)‐tuned magnesium single‐atom catalyst (Mg‐SAC) is developed. Remarkably, this catalyst achieved a CO Faraday efficiency of 97.3% and a current density of 260.4 mA cm −2 at −0.4 V vs the reversible hydrogen electrode in a flow cell, surpassing the performance of most state‐of‐the‐art SACs and transition metal catalysts reported in the literature. Mechanistic studies reveal that * CO desorption on Mg sites is significantly easier compared to that on Fe and Co sites. Furthermore, the incorporation of F atoms modifies the electronic structure of the MgN 4 sites, substantially lowering the energy barrier for the formation of the critical * COOH intermediate.

No abstract available

Iron‐nitrogen‐carbon (Fe‐N‐C) materials are promising non‐precious metal catalysts for the oxygen reduction reaction (ORR), yet their long‐term stability remains a critical challenge due to the dissolution of Fe‐based active sites and corrosion of the carbon support. Here, a Fe‐Zr dual‐atom carbon‐based catalyst (Fe,Zr‐NC) via a one‐step solid‐state synthesis method is reported. The introduction of atomically dispersed Zr–N units adjacent to Fe–N4 centers creates a dual‐metal coordination structure that modulates the local electronic environment of Fe and weakens *OH adsorption, which is the rate‐limiting step in the ORR process. Density functional theory (DFT) calculations reveal that the Fe–Zr synergy positions the catalyst near the apex of the ORR activity volcano. Extended experimental EXAFS confirms a Fe–Zr distance of ≈3.30 Å, closely matching the theoretical optimum (≈3.39 Å). As a result, Fe, Zr‐NC achieves a high half‐wave potential (0.891 V vs reversible hydrogen electrode (RHE)) with negligible activity loss over 5000 cyclic voltammetry cycles, outperforming commercial Pt/C. In zinc–air batteries, the catalyst delivers a peak power density of 185.7 mW cm−2 and operates stably for over 453 h. This work highlights the importance of dual‐atom synergy in tuning intermediate binding energies and provides design principles for next‐generation ORR electrocatalysts.

Single-atom catalysts (SACs) are regarded as promising photocatalysts due to their maximized atomic utilization efficiency. However, achieving stable and efficient SACs remains challenging owing to the strong aggregation tendency of metal atoms. In this study, CoAl-layered double hydroxide (LDH) is used as a support, with metal vacancies introduced on its surface by controlling the material thickness. Ru atoms are anchored at these vacancy sites, achieving atomic-level dispersion and effectively preventing aggregation into clusters. The Ru single atom formed an unsaturated coordination environment with the LDH support, where the unsaturated coordination around Ru markedly enhanced CO2 adsorption and activation. Meanwhile, these well-dispersed active centers generate a high density of catalytically active sites, which effectively modulate the spatial distribution of photogenerated charges across the catalyst surface. The results demonstrate that the ultrathin LDH loaded with 1.0 wt% Ru photocatalyst achieves a CO production rate of 4663.34 µmol g-1 h-1, nearly doubling the performance of bulk LDH loaded with 1.0wt% Ru. Density functional theory (DFT) calculations further confirm that u-1.0wt%Ru-LDH effectively stabilizes the COOH* intermediate, reducing the energy barrier for protonation and accelerating the CO2 reduction reaction. This study offers insights into single-atom photocatalyst design and underscores the potential of single-atom engineering for photocatalysis.

Electroreduction of CO2 into high‐value chemicals and fuels driven is an effective way to alleviate the environmental crisis, but it suffers from poor activity and low selectivity of the catalyst. Single‐atom catalysts have excellent selectivity and the highest atomic efficiency, and are widely used in the 2‐electron transfer to produce CO. However, electroreduction of CO2 to C2+ products involves complex processes such as multi‐electron reaction and competitive adsorption, so single‐atom catalysis is often powerless. Herein, a single‐atom Ga‐anchored F‐doped Cu2O catalyst with dual active sites is reported. The Lewis acid‐base pairs and Ga single atom sites promote the adsorption/activation of CO2 and the dissociation of water molecules, respectively, enhance the coverage of *CO and *H, and their synergy optimizes the reaction path. At a high current density of 600 mA cm−2, the FEC2+ reached 72.8 ± 3.2% with remarkable stability. Experiments and theory calculations demonstrate that the dual sites increase the coverage of *CO and *H, and the key intermediate *CO is transformed into *CHO through protonation reaction, which changes the reaction path from the C─C coupling (*OCCO) to the protonation followed by C─C coupling (*OCCHO) with low energy barrier, greatly improving the selectivity for C2+ products.

No abstract available

Single-atom alloy (SAA) catalysts exhibit huge potential in heterogeneous catalysis. Manufacturing SAAs requires complex and expensive synthesis methods to precisely control the atomic scale dispersion to form diluted alloys with less active sites and easy sintering of host metal, which is still in the early stages of development.  Here, we address these limitations with a straightforward strategy from a brand-new perspective involving the 'islanding effect' for manufacturing SAAs without dilution: homogeneous RuNi alloys were continuously refined to highly dispersed alloy-islands (~ 1 nm) with completely single-atom sites where the relative metal loading was as high as 40%. Characterized by advanced atomic-resolution techniques, single Ru atoms were bonded with Ni as SAAs with extraordinary long-term stability and no sintering of the host metal. The SAAs exhibited 100% CO selectivity, over 55 times reverse water-gas shift (RWGS) rate than the alloys with Ru cluster sites, and over 3-4 times higher than SAAs by the dilution strategy. This study reports a one-step manufacturing strategy for SAA's using the wetness impregnation method with durable high atomic efficiency and holds promise for large-scale industrial applications.

Single‐atom catalysts have attracted extensive attention due to their unique atomic structures and extraordinary activities in catalyzing chemical reactions. However, the lack of general and efficient approaches for producing high‐density single atoms on suitably tailored supporting matrixes hinders their industrial applications. Here, a rapid melt‐quenching strategy with high throughput to synthesize single atoms with high metal‐atom loadings of up to 9.7 wt% or 2.6 at% on nanoporous metal compounds is reported, representing several‐fold improvements compared to benchmarks in the literature. Mechanism characterizations reveal that the high‐temperature melting provides the essential liquid environment and activation energy to achieve the atomization of metals, while the following rapid‐quenching pins the isolated metal atoms and stabilizes the coordination environment. In comparison with carbon‐supported single‐atom catalysts, various collaboration combinations of single atoms and nanoporous metal compounds can be synthesized using the strategy, thus achieving efficient hydrazine oxidation‐assisted H2 production. This synthesis protocol is highly compatible with automatic operation, which provides a feasible and general route to design and manufacture specific single‐atom catalysts with tunable atomic metal components and supporting matrixes, thus promoting the deployment of single‐atom catalysts for various energy technology applications.

Owing to the remarkable catalytic attributes, single-atom catalysts (SACs) have exhibited promising application prospects as the substitutes of natural enzymes. However, the low loading amount of atomic sites on typical SACs (no more than 5 wt %) significantly restricts their increased capability. Hereby, a layer growth inhibitor protocol was attempted to optimize anchoring isolated Co atoms efficiently on ultrathin monolayer layered double hydroxides (LDHs). Superior to the conventional multiple-layer LDHs, the synthesized monolayer LDHs (7.29 nm-thick) served as the emerging support for dispersing substantial active sites and featured a dramatic loading content of 32.5 wt %. Through X-ray absorption spectroscopy, the atomically dispersed active centers on Co SACs were verified as Co-N4 moieties. The results of radical scavenger experiments and electron paramagnetic resonance spectroscopy showed that Co SACs were favorable to the high yield of reactive oxygen species originating from the decomposition of H2O2. Therefore, Co SACs functioned as a sensitive enhancer to drastically boost the luminol-H2O2 chemiluminescence intensity by ∼4713-fold, which excelled drastically over these previously reported SACs. Furthermore, Co SACs were adopted as chemiluminescent probes for the quantitation of chlorothalonil, wherein a low detection limit of 49 pg mL-1 (3σ) was achieved. Additionally, the successful application in recovery trials demonstrated the favorable feasibility of Co SACs. The facile layer growth inhibitor protocol affords SACs with improved loading properties and even superior catalytic performances for sensitive luminescent bioassays.

Single-atom catalysts (SACs) have attracted much interest for electrochemical CO2 reduction because of their high metal utilization and excellent catalytic activity. However, the practical applications of SACs were restricted by the low production yield. Herein, we developed a facile synthetic strategy for fabricating metal-nitrogen-carbon nanotube (M-N-CNT, M = Ni, Co, Cu, Fe, Mn, Zn, Pt, or Ru) SACs at scale (>1 g) by direct pyrolysis of metal cations, phenanthroline and CNTs at high temperature. The pyrolysis leads to forming coordinated Ni-N active sites anchored on CNTs. The prepared Ni-N-CNT catalyst with a remarkable Ni loading of 2 wt% determined by ICP exhibits the highest activity for CO2-to-CO conversion with a high faradaic efficiency of 94% and excellent stability. Aberration-corrected high-angle annular dark-field transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray absorption spectroscopy confirm the presence of isolated Ni single atoms in Ni-N-CNT, which act as the active centers for CO2 electroreduction while the CNT support offers fast pathways for electron and mass transports. This work laid foundations for future practical applications in CO2 electroreduction, oxygen reduction reactions, water splitting and nitrogen reduction and beyond.

No abstract available

Controllable synthesis of single atom catalysts (SACs) with high loading remains challenging due to the aggregation tendency of metal atoms as the surface coverage increases. Here we report the synthesis of graphene supported cobalt SACs (Co1/G) with a tuneable high loading by atomic layer deposition. Ozone treatment of the graphene support not only eliminates the undesirable ligands of the pre-deposited metal precursors, but also regenerates active sites for the precise tuning of the density of Co atoms. The Co1/G SACs also demonstrate exceptional activity and high selectivity for the hydrogenation of nitroarenes to produce azoxy aromatic compounds, attributable to the formation of a coordinatively unsaturated and positively charged catalytically active center (Co–O–C) arising from the proximal-atom induced partial depletion of the 3d Co orbitals. Our findings pave the way for the precise engineering of the metal loading in a variety of SACs for superior catalytic activities. Controllable synthesis of single atom catalysts with sufficiently high metal loading remains challenging due to the tendency of agglomeration. Here the authors synthesize a series of stable atomically dispersed cobalt atoms on graphene with high Co loadings via the regeneration of active sites by atomic layer deposition.

Atomically dispersed Pt-group metals are promising as nanocatalysts because of their unique geometric structures and ultrahigh atomic utilization. However, loading isolated Pt-group metals in single-atom alloys (SAAs) with distinctive bimetallic sites is challenging. In this study, we present amorphous mesoporous Ni boride (Ni-B) as an ideal substrate to uniformly disperse Pt atoms with tunable loadings (1.7 to 12.2 wt %). The effect of the morphology, composition, and crystal phase of the Ni-B host on the growth and dispersion of Pt atoms is discussed. The resulting amorphous Pt-Ni-B mesoporous nanospheres exhibit superior electrocatalytic H2 evolution performance in acidic media. This strategy holds the potential to synthesize a diverse library of mesoporous amorphous Pt-group SAAs, by leveraging functional amorphous nanostructured 3d transition-metal borides as substrates, thereby proposing a comprehensive strategy to control atomically dispersed Pt-group metals.

Single metal atom isolated in nitrogen‐doped carbon materials (MNC) are effective electrocatalysts for oxygen reduction reaction (ORR), which produces H2O2 or H2O via 2‐electron or 4‐electron process. However, most of MNC catalysts can only present high selectivity for one product, and the selectivity is usually regulated by complicated structure design. Herein, a carbon black‐supported CoNC catalyst (CB@CoNC) is synthesized. Tunable 2‐electron/4‐electron behavior is realized on CB@Co‐N‐C by utilizing its H2O2 yield dependence on electrolyte pH and catalyst loading. In acidic media with low catalyst loading, CB@CoNC presents excellent mass activity and high selectivity for H2O2 production. In flow cell with gas diffusion electrode, a H2O2 production rate of 5.04 mol h−1 g−1 is achieved by CB@CoNC on electrolyte circulation mode, and a long‐term H2O2 production of 200 h is demonstrated on electrolyte non‐circulation mode. Meanwhile, CB@CoNC exhibits a dominant 4‐electron ORR pathway with high activity and durability in pH neutral media with high catalyst loading. The microbial fuel cell using CB@CoNC as the cathode catalyst shows a peak power density close to that of benchmark Pt/C catalyst.

Surface-supported isolated atoms in single-atom catalysts (SACs) are usually stabilized by diverse defects. The fabrication of high-metal-loading and thermally stable SACs remains a formidable challenge due to the difficulty of creating high densities of underpinning stable defects. Here we report that isolated Pt atoms can be stabilized through a strong covalent metal-support interaction (CMSI) that is not associated with support defects, yielding a high-loading and thermally stable SAC by trapping either the already deposited Pt atoms or the PtO2 units vaporized from nanoparticles during high-temperature calcination. Experimental and computational modeling studies reveal that iron oxide reducibility is crucial to anchor isolated Pt atoms. The resulting high concentrations of single atoms enable specific activities far exceeding those of conventional nanoparticle catalysts. This non defect-stabilization strategy can be extended to non-reducible supports by simply doping with iron oxide, thus paving a new way for constructing high-loading SACs for diverse industrially important catalytic reactions.Developing stable single-atom catalysts (SACs) with a high metal loading remains a challenge due to the difficulty of creating high densities of defects on support materials. Here the authors prepare Pt SACs with high Pt loadings by virtue of strong covalent metal-support interaction, rather than support defects.

Graphdiyne (GDY) has achieved great success in the application of two-dimensional carbon materials in recent years due to its excellent electrochemical catalytic capacity. Considering the unique electronic structure of GDY, transition metal (TM1) (TM = Fe, Ru, Os, Co, Rh, Ir) single-atom catalysts (SACs) with isolated loading on GDY were designed for electrochemical CO2 reduction reaction (CO2RR) with density functional theoretical (DFT) calculations. The charge density difference and projected densities of states have been systematically calculated. The mechanism of electrochemical catalysis and the reaction pathway of CO2RR over Os1/GDY catalysts have also been investigated and high catalytic activity was found for the generation of methane. The calculated results provide a theoretical basis for the design of efficient GDY-based SACs for electrochemical CO2RR.

No abstract available

Understanding the dynamic evolution of Cu species under varying environmental conditions is critical for addressing challenges related to the activity and the stability of copper-based catalysts in thermo-, photo-, and electrocatalysis. However, metal-metal interactions between dual single atoms and their effects on Cu evolution after exposure to different environmental molecules remain underexplored. Herein, we synthesized bimetallic Cu-Y/Beta catalysts with dual single-atom Cu and Y sites and monometallic Cu-Beta catalysts with isolated Cu sites in dealuminated Beta zeolites. By varying Cu and Y compositions, diatomic interactions were studied under H2 and ethanol atmospheres. With 6 wt% Y loading, approximately 0.4 wt% of Cu species in Cu-Y/Beta remained partially oxidized as Cu(I) after reduction in pure H2 at 350 °C, in contrast to the full transition to metallic Cu observed in Cu-Beta. Combining X-ray absorption spectroscopy with kinetic studies revealed that metallic Cu became the predominant species after reduction with H2 as Cu loading increased from 0.4 to 1.7 wt%, quadrupling the initial ethanol dehydrogenation rate and demonstrating the dominant role of Cu(0) sites. Scanning transmission electron microscopy and density functional theory simulations indicated spatial proximity between dual single-atom Cu and Y sites and elucidated Cu speciation controlled by diatomic interactions.

Single-atom catalysts have drawn great attention, especially in electrocatalysis. However, most of previous works focus on the enhanced catalytic properties via improving metal loading. Engineering morphologies of catalysts to facilitate mass transport through catalyst layers, thus increasing the utilization of each active site, is regarded as one appealing way for enhanced performances. Herein, as a proof-of-concept research, we design, for the first time, an overhang-eave structure decorated with isolated single-atom iron sites via a silica-mediated MOF-templated (SMMT) approach for oxygen reduction reaction (ORR) catalysis. This catalyst demonstrates superior ORR performances in both alkaline and acidic electrolytes, comparable to the state-of-the-art Pt/C catalyst and superior to most of the precious-metal-free catalysts reported to date. This superior activity originates from its edge-rich structure, having more three-phase boundaries with enhanced mass transport of reactants to accessible single-atom iron sites (that is, increasing the utilization of active sites), which verifies the practicability of such synthetic approach .

The design of an efficient catalytic system with low Pt loading and excellent stability for the acidic oxygen reduction reaction is still a challenge for the extensive application of proton-exchange membrane fuel cells. Here, a gas-phase ordered alloying strategy is proposed to construct an effective synergistic catalytic system that blends PtM intermetallic compounds (PtM IMC, M = Fe, Cu, and Ni) and dense isolated transition metal sites (M-N4 ) on nitrogen-doped carbon (NC). This strategy enables Pt nanoparticles and defects on the NC support to timely trap flowing metal salt without partial aggregation, which is attributed to the good diffusivity of gaseous transition metal salts with low boiling points. In particular, the resulting Pt1 Fe1 IMC cooperating with Fe-N4 sites achieves cooperative oxygen reduction with a half-wave potential up to 0.94 V and leads to a high mass activity of 0.51 A  mgPt -1 and only 23.5% decay after 30 k cycles, both of which exceed DOE 2025 targets. This strategy provides a method for reducing Pt loading in fuel cells by integrating Pt-based intermetallics and single transition metal sites to produce an efficient synergistic catalytic system.

No abstract available

Carbon supports containing single-atomically dispersed metal-Nx (denoted as MSAC-NxCy, x, y: coordination number) have attracted increasing attention due to their superb performance in heterogeneous catalysis. However, large-scale controllable preparation of single-atom catalysts (SACs) with high concentration of supported metal-Nx is still a big challenge because of the metal atom agglomeration during synthesis at high density and temperatures. Herein, we report a stepwise anchoring strategy from a 1,10-o-phenanthroline Pt chelate to an Nx-doped carbon (NxCy) with isolated Pt single-atom catalysts (PtSAC-NxCy) containing Pt loadings up to 5.31 wt % measured via energy-dispersive X-ray spectroscopy (EDS). The results show that 1,10-o-phenanthroline Pt chelate predominantly contributes to the formation of chelate single metal sites that bind tightly to platinum ions to prevent metal atoms from aggregating, resulting in high metal loading. The high-loading PtSAC-NxCy exhibits a low hydrogen evolution (HER) overpotential of 24 mV at 0.010 A cm-2 current density with a relatively small Tafel gradient of 60.25 mV dec-1 and excellent stable performance. In addition, the PtSAC-NxCy catalyst shows excellent oxygen reduction reaction (ORR) catalytic activity with good stability, represented by the fast ORR kinetics under high-potential conditions. Theoretical calculations show that PtSAC-NC3 (x = 1, y = 3) offers a lower H2O activation energy barrier than Pt nanoparticles. The adsorption free energy of a H atom on a Pt single-atom site is lower than that on a Pt cluster, which is easier for H2 desorption. This study provides a potentially powerful cascade anchoring strategy in the design of other stable MSAC-NxCy catalysts with high-density metal-Nx sites for the HER and ORR.

Single-atom catalysts often show exceptionally high performance per metal loading. However, the isolated atom sites tend to agglomerate during preparation and/or high-temperature reaction. Here we show that in the case of Rh/Al2O3 this deactivation can be prevented by dissolution/exsolution of metal atoms into/from the support. We design and synthesise a series of single-atom catalysts, characterise them and study the impact of exsolution in the dry reforming of methane at 700–900 °C. The catalysts' performance increases with increasing reaction time, as the rhodium atoms migrate from the subsurface to the surface. Although the oxidation state of rhodium changes from Rh(iii) to Rh(ii) or Rh(0) during catalysis, atom migration is the main factor affecting catalyst performance. The implications of these results for preparing real-life catalysts are discussed.

Improving metal loading and controlling the coordination environment is nontrivial and challenging for single‐atom catalysts (SACs), which have the greatest atomic efficiency and largest number of interface sites. In this study, a matching bidentate ligand (MBL) anchoring strategy is designed for the construction of CuN4 SACs with tunable coordination environments (Cu loading range from 0.4 to15.4 wt.%). The obtained Cu SA/ZIF and Cu SA/ZIF* (0.4 wt.%) (ZIF and ZIF* = Zeolitic imidazolate framework with Matching bidentate N‐ligands) nanocomposites exhibit superior performance in homo‐coupling of phenyl acetylene under light irradiation (TON = 580, selectivity > 99%), which is 22 times higher than that of Cu SA/NC‐800 (NC = N‐doped porous carbon). Experiments and density functional theory calculations confirmed that the specific Cu five‐membered ring formed using the MBL anchoring strategy is the key to the immobilization of isolated Cu atoms. This strategy provides a basis for the construction of M SA/MOF, which has the potential to narrow the gap between experimental and theoretical catalysis, as further confirmed by the successful preparation of Fe SA/ZIF and Ni SA/ZIF.

Maximum atom efficiency as well as distinct chemoselectivity is expected for electrocatalysis on atomically dispersed (or single site) metal centres, but its realization remains challenging so far, because carbon, as the most widely used electrocatalyst support, cannot effectively stabilize them. Here we report that a sulfur-doped zeolite-templated carbon, simultaneously exhibiting large sulfur content (17 wt% S), as well as a unique carbon structure (that is, highly curved three-dimensional networks of graphene nanoribbons), can stabilize a relatively high loading of platinum (5 wt%) in the form of highly dispersed species including site isolated atoms. In the oxygen reduction reaction, this catalyst does not follow a conventional four-electron pathway producing H2O, but selectively produces H2O2 even over extended times without significant degradation of the activity. Thus, this approach constitutes a potentially promising route for producing important fine chemical H2O2, and also offers opportunities for tuning the selectivity of other electrochemical reactions on various metal catalysts. Atomically dispersed metal catalysts display high atom efficiency for electrocatalytic processes. Here, the authors report that sulfur-doped zeolite-templated carbon stabilizes highly dispersed platinum species, predominantly as single-atom centres, and probe its oxygen reduction selectivity.

The renewable-electricity-powered carbon dioxide reduction (eCO2R) to value-added fuels and feedstocks like methane (CH4) holds the sustainable and economically viable carbon cycle at meaningful scales. However, this kinetically challenging eight-electron multistep deep-reduction encounters insufficient catalyst design principles to steer complex CO2 reduction pathways. Utilizing atomic copper (Cu) structures with unitary active site can boost eCO2R-to-CH4 selectivity due to the efficient suppression of unwanted C-C coupling. Herein, we report a sequential ion exchange strategy to fabricate periodic Cu single-atom catalysts within a polymeric carbon nitride (PCN) matrix, where the uniformly dispersed, diagonally coordinated N-Cu-N configuration hosts low-valent Cuδ+ centers. Leveraging the periodic N-anchoring sites with delocalized π-electron conjugation in PCN matrix, the isolated Cu sites are obtained with an interatomic distance of ~4.2 Å under high metal-loading conditions. This engineered spatial configuration effectively inhibits C-C coupling to avoid subsequent multicarbon products formation. The optimized Cu1/PCN demonstrates exceptional eCO2R-to-CH4 performance, achieving 71.1% CH4 Faradaic efficiency with a high partial current density of 426.6 mA cm-2 at -1.50 V vs. reversible hydrogen electrode, outpacing the state-of-the-art catalysts. This work delves into effective concepts for steering desirable reaction pathways via precisely modulating active site structures at the atomic level to create favorable microenvironments.

Cost-effective preparation of efficient electrocatalysts is vitally important for energy storage and conversion. Here, a facile chemical activation strategy using biomass cellulose as the carbon feedstock to fabricate isolated Fe atoms dispersed on a nitrogen doped graphene/nanocarbon hybrid is reported. This new single atom catalyst aFe-NGC worked as an excellent electrocatalyst towards the ORR compared to commercial Pt/C with 30 mV higher positive half-wave potential, larger current density, better stability and stronger methanol-tolerance. The key active sites for enhancing the ORR activity originated from the constructed high loading Fe-N/C configuration coupled with doped nitrogens, as explored by optimizing the activation temperatures and characterized by state-of-the-art techniques including aberration-corrected STEM and synchrotron XANES. This strategy could be developed into a general approach to prepare highly efficient atomic metal electrocatalysts using abundant biomass as a cost-effective carbon source.

Precisely tailoring the molecular configurations of single-atom sites and elucidating their correlation with generated specific reactive species is crucial for advancing Fenton-like chemistry toward targeted remediation. Herein, we developed a facile approach to precisely modulate the distances between isolated Fe‒N4 sites (dFe-Fe) from nanometer (0.95 nm) to subnanometer (0.43 nm) to construct a family of well-defined Fe‒N4 twins with manipulated ligand-field strength and spin states. Different Fe‒N4 twin sites trigger a metal-loading-independent volcano-shaped Fenton-like activity trend. The optimal configuration, achieved at an Fe‒Fe distance of 0.43 nm (Fed0.43SA), induces an intermediate-spin (t2g4eg1) configuration that optimizes eg orbital occupancy, thereby promoting peroxymonosulfate (PMS) adsorption to form *HSO5 - and subsequently lowers the energy barrier for coupling with another PMS to selectively generate singlet oxygen (1O2). The robust molecular catalyst with Fe‒N4 twin sites sustains over 120 h of continuous treatment of organic wastewater and demonstrates simultaneous disinfection and pharmaceutical removal of actual hospital wastewater. This work presents an advanced strategy for engineering single-atom sites with multi-site cooperativity to regulate Fenton-like catalysis, enabling rapid and real-world water purification.

Metal single atom (MSA) materials exhibit excellent properties and are receiving widespread interest for their effectiveness in promoting a variety of catalytic reactions. The current strategies for preparing MSA catalysts involve complicated operation flows and suffer from low loading of the single atoms prepared, owing to the surface defect density of the substrate. In this paper, we report a simple physical method for preparing high-density copper single atom catalysts on amorphous carbon by Coulomb explosion. The results of the in situ observation showed that copper atoms on particle surfaces were emitted under electron beam irradiation and were captured by defects in a surrounding amorphous carbon film as isolated single atoms. By controlling the time and intensity of the Coulomb explosion, the ratio of copper single atoms to clusters aggregated from single atoms on the amorphous carbon can be controlled. Our work will provide new ideas for a universal simple physical preparation of MSA catalysts.

Ammonia synthesis is a cornerstone in the chemical industry. Given the traditional Haber-Bosch (H-B) process requires very high temperature and pressure, it is imperative to develop catalysts capable of facilitating ammonia synthesis under mild conditions. In this work, a post-metal replacement strategy is developed to improve the Fe loading in single-atom Fe-implanted N-doped carbon catalysts. Starting from the Zn-Fe-N-C material with single-atom Zn and Fe sites coexisting in N-doped porous carbon pyrolyzed from porphyrinic metal-organic frameworks (MOFs), the replacement of single-atom Zn with Fe sites is performed, which significantly increases the Fe loading from 1.33 wt% to 2.39 wt%. This effectively suppresses the migration and agglomeration of Fe, yielding Fe-N-C with high metal loading (FeHL-N-C). Notably, the FeHL-N-C catalyst exhibits a catalytic rate of 558 μmol·gcat-1·h-1 at 300 °C for ammonia synthesis at atmospheric pressure, far surpassing the performance of the traditional dominant fused iron and even Ru-based precious metal catalysts.

Aiming to improve the photocatalytic activity in N2 fixation to produce ammonia, herein, we proposed a photochemical strategy to fabricate defects, and further deposition of Ru single atoms onto UiO-66 (Zr) framework. Electron-metal-support interactions (EMSI) were built between Ru single atoms and the support via a covalently bonding. EMSI were capable of accelerating charge transfer between Ru SAs and UiO-66, which was favorable for highly-efficiently photocatalytic activity. The photocatalytic production rate of ammonia improved from 4.57 μmol g-1 h-1 to 16.28 μmol g-1 h-1 with the fabrication of defects onto UiO-66, and further to 53.28 μmol g-1 h-1 with Ru-single atoms loading. From the DFT results, it was found that d-orbital electrons of Ru were donated to N2 π∗-antibonding orbital, facilitating the activation of the N≡N triple bond. A hybrid distal-alternating reaction pathway was probably occurred for the photocatalytic N2 reduction to ammonia on Ru1/d-UiO-66 (single Ru sites decorated onto the nodes of defective UiO-66), and the first step of hydrogenation of N2 was the reaction determination step. This work shed a light on improving the photocatalytic activity via feasibly anchoring single atoms on MOF, and provided more evidences to understand the reaction mechanism in photocatalytic reduction of N2.

Photocatalytic nitrogen fixation offers a sustainable pathway for green ammonia synthesis under mild conditions, yet its practical application is hindered by the inefficient charge separation and insufficient active sites of conventional photocatalysts. Herein, we present a rationally engineered heterostructure comprising Pt single atoms (PtSAs) on nano metal-organic frameworks (MOF-74)/hollow double-shelled tubular C3N4 (TCN), which addresses these limitations through synergistic effects. The Z-scheme heterojunction formed between MOF-74 and TCN establishes a built-in electric field, facilitating directional electron transfer from MOF-74 to PtSAs-modified TCN. PtSAs anchored through PtN coordination on TCN act as efficient electron traps, effectively suppressing charge carrier recombination. Furthermore, the nanoscale MOF-74 (<20 nm) enhances N2 adsorption by quantum confinement effects, thereby addressing the challenge of limited active sites. The photocatalytic ammonia generation rate of optimized Pt@MOF/TCN composite achieved a high ammonia production rate of 544.91 μmol g-1 h-1 under visible light illumination, which surpasses most reported photocatalysts. This study provides novel insights into the fundamental design principles of high-efficiency photocatalysts through atomic-level engineering and heterostucture construction.

Single‐atom catalysts (SACs) have received significant interest for optimizing metal atom utilization and superior catalytic performance in hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR). In this study, we investigate a range of single‐transition metal (STM1 = Sc1, Ti1, V1, Cr1, Mn1, Fe1, Co1, Ni1, Cu1, Zr1, Nb1, Mo1, Ru1, Rh1, Pd1, Ag1, W1, Re1, Os1, Ir1, Pt1, and Au1) atoms supported on graphyne (GY) surface for HER/OER and ORR using first‐principle calculations. Ab initio molecular dynamics (AIMD) simulations and phonon dispersion spectra reveal the dynamic and thermal stabilities of the GY surface. The exceptional stability of all supported STM1 atoms within the H1 cavity of the GY surface exists in an isolated form, facilitating the uniform distribution and proper arrangement of single atoms on GY. In particular, Sc1, Co1, Fe1, and Au1/GY demonstrate promising catalytic efficiency in the HER due to idealistic ΔGH* values via the Volmer‐Heyrovsky pathway. Notably, Sc1 and Au1/GY exhibit superior HER catalytic activity compared to other studied catalysts. Co1/GY catalyst exhibits higher selectivity and activity for the OER, with an overpotential (0.46 V) comparable to MoC2, IrO2, and RuO2. Also, Rh1 and Co1/GY SACs exhibited promising electrocatalysts for the ORR, with an overpotential of 0.36 and 0.46 V, respectively. Therefore, Co1/GY is a versatile electrocatalyst for metal‐air batteries and water‐splitting. This study further incorporates computational analysis of the kinetic potential energy barriers of Co1 and Rh1 in the OER and ORR. A strong correlation is found between the estimated kinetic activation barriers for the thermodynamic outcomes and all proton‐coupled electron transfer steps. We establish a relation for the Gibbs free energy of intermediates to understand the mechanism of SACs supported on STM1/GY and introduce a key descriptor. This study highlights GY as a favorable single‐atom support for designing highly active and cost‐effective versatile electrocatalysts for practical applications.

The present work investigated the binding of atomically dispersed transition metals to the 2D fullerene quasihexagonal phase C60 (qhp‐C60) framework and the catalytic performance of the corresponding single/dual‐sided single‐atom catalysts for CO electroreduction by means of density functional theory calculations. Compared to isolated C60 molecules, the qhp‐C60 framework not only effectively inhibits metal aggregation through its unique confining nanocages and stronger metal–substrate interactions, but also enhances the catalytic activity and selectivity by a more efficient electron‐buffering effect. Among all the metal centers examined, Mn was identified as the most promising candidate for selective CO‐to‐methane conversion.

Photocatalytic nitrogen fixation is a promising method for solving energy crisis and environmental problems. In this study, a straightforward approach to synthesize a single‐atom catalyst CZ‐1.5. The catalyst is developed through the formation of covalent bonds between copper atoms and a metal‐organic framework (MOF). The experimental data have demonstrated that Cu binds to the MOF through the N on the ligand and the defect sites on the Zr oxide cluster. The CZ‐1.5 shows the best nitrogen photofixation performance under ambient conditions and reaches 199.30 µmol g⁻¹ h⁻¹, which is 1.47 times than that of Zr‐MOF. Density functional theory calculation combined with X‐ray Absorption Fine Structure results reveal the possible hydrogenation pathway of single‐atom active site. This work provides a new approach for the design of non‐precious‐metal single‐atom photocatalysts that single atoms are bound to organic ligands and oxidation cluster defects of MOFs, which contribute to the advancement of sustainable development.

An environmental-friendly and sustainable carbon-based host is one of the most competitive strategies for achieving high loading and practicality of Li-S batteries. However, the polysulfide conversion reaction kinetics is still limited by the nonuniform or monofunctional catalyst configuration in the carbon host. In this work, we propose a catalysis mode based on "relay-type" co-operation by adjacent dual-metal single atoms for high-rate and durable Li-S batteries. A discarded sericin fabric-derived porous N-doped carbon with a stacked schistose structure is prepared as the high-loading sulfur (84 wt %) host by a facile ionothermal method, which further enables the uniform anchoring of Fe/Co dual-metal single atoms. This multifunctional host enables superior lithiophilic-sulfiphilic and electrocatalytic capabilities contributed by the "relay-type" single-atom modulation effects on different conversion stages of liquid polysulfides and solid Li2S2/Li2S, leading to the suppression of the "shuttle effect", alleviation of nucleation and decomposition barriers of Li2Sx, and acceleration of polysulfide conversion kinetics. The corresponding Li-S batteries exhibit a high specific capacity of 1399.0 mA h g-1, high-rate performance up to 10 C, and excellent cycling stability over 1000 cycles. They can also endure the high sulfur loading of 8.5 mg cm-2 and the lean electrolyte condition and yield an areal capacity as high as 8.6 mA h cm-2. This work evidentially demonstrates the potential of waste biomass reutilization coupled with the design of a single-atom system for practical Li-S batteries with high energy density.

Single‐atom catalysts (SACs) with a maximum atom utilization efficiency have received growing attention in heterogeneous catalysis. The supporting substrate that provides atomic‐dispersed anchoring sites and the local electronic environment in these catalysts is crucial to their activity and stability. Here, inspired by N‐doped graphene substrate, the role of N is explored in transition metal nitrides for anchoring single metal atoms toward single‐atom catalysis. A pore‐rich metallic vanadium nitride (VN) nanosheet is fabricated as one supporting‐substrate example, whose surface features abundant unsaturated N sites with lower binding energy than that of widely used N‐doped graphene. Impressively, it is found that this support can anchor nearly all platinum‐group single atoms (e.g., platinum, palladium, iridium, and ruthenium), and even be extendable to multiple SACs, i.e., binary (Pt/Pd) and ternary (Pt/Pd/Ir). As a proof‐of‐concept application for hydrogen production, Pt‐based SAC (Pt1‐VN) performs excellently, exhibiting a mass activity up to 22.55 A mg−1Pt at 0.05 V and a high turnover frequency value close to 0.350 H2 s−1, superior to commercial platinum/carbon catalyst. The catalyst's durability can be further improved by using binary (Pt1Pd1‐VN) SAC. This work provides inexpensive and durable nitride‐based support, giving a possible pathway for universally constructing platinum‐group SACs.

Controlling the chemical environments of the active metal atom including both coordination number (CN) and local composition (LC) is vital to achieve active and stable single-atom catalysts (SACs), but remains challenging. Here we synthesized a series of supported Pt1 SACs by depositing Pt atoms onto the pretuned anchoring sites on nitrogen-doped carbon using atomic layer deposition. In hydrogenation of para-chloronitrobenzene, the Pt1 SAC with a higher CN about four but less pyridinic nitrogen (Npyri) content exhibits a remarkably high activity along with superior recyclability compared to those with lower CNs and more Npyri. Theoretical calculations reveal that the four-coordinated Pt1 atoms with about 1 eV lower formation energy are more resistant to agglomerations than the three-coordinated ones. Composition-wise decrease of the Pt-Npyri bond upshifts gradually the Pt-5d center, and minimal one Pt-Npyri bond features a high-lying Pt-5d state that largely facilitates H2 dissociation, boosting hydrogenation activity remarkably.

The rational design and fabrication of platinum group metal-free (PGM-free) electrocatalysts for oxygen reduction reaction (ORR) via economically feasible approach is essential for reducing the cost of fuel cells and metal-air batteries. Catalysts must have very high activity, and excellent mass diffusion of reactants. Herein, we display a high-performing dual-metal single atom catalyst (DM-SAC) composed of Fe and Ni SA active sites immobilized in porous carbon nanospheres (Fe/Ni-N-PCS), prepared via defects/vacancies anchoring strategy. The abundant and accessible edge-hosted Fe and Ni SA active sites can promote the adsorption/desorption behavior for ORR intermediates attributing to possible synergistic effects between dual-metal SA active sites. Thus, the as-developed Fe/Ni-N-PCS DM-SAC exhibits impressive ORR electrocatalytic performance in both alkaline (Eonset = 1.04 V, E1/2 = 0.9 V) and acid solutions (Eonset = 0.87 V, E1/2 = 0.71 V), and high stability, outperforming SACs with solo Fe-Nx or Ni-Nx active sites, and benchmark PGM. Fe/Ni-N-PCS also exhibits superior oxygen evolution reaction (OER) performance with low overpotential and long-term stability. Zn-air battery with Fe/Ni-N-PCS cathode yields encouraging performance, including working potential, peak power density, and the stability of charge and discharge cycles. Our synthesis method may promote the fabrication of other DM-SAC and the great promise in practical applications.

In the context of reshaping the energy pattern, designing and synthesizing high‐performance noble metal‐free photocatalysts with ultra‐high atomic utilization for hydrogen evolution reaction (HER) still remains a challenge. In a streamlined synthesis process, in‐situ single atom anchoring is performed in parallel with HER by irradiating a precursory defect‐state CdS/Co suspension (Co‐DCdS‐Ss) system under simulated sunlight and the in‐situ synthesizing single‐atom Co photocatalyst (Co5:DCdS) exhibits further improved catalytic performance (60.10 mmol g−1 h−1) compared with Co‐DCdS‐Ss (18.09 mmol g−1 h−1), reaching an apparent quantum yield of 57.6% at 500 nm and a solar‐chemical energy conversion efficiency (SCC) of 6.26% at AM 1.5G. In‐depth characterization tests and density functional theory (DFT) calculations prove that the anchoring of Co single atom deepens the asymmetric charge distribution of the two‐coordination S atom adjacent to the cadmium vacancy (VCd). The synergy between electron delocalization VCd and Co single atom on the catalyst surface is constructed, which bifunctional sites responsible for boosting water adsorption‐dissociation and hydrogen evolution. This study advances the understanding of the underlying mechanisms of synergy between surface defects and metal single atoms and opens a new horizon for the development of advanced materials in the field of photocatalysis.

It is crucial to break the low metal-loading limitation and reveal the intersite synergy-governed catalytic behavior of single-atom catalysts (SACs). Here, a universal synthesis strategy achieves record loadings of transition metals (Fe 41.31 wt%, Mn 35.13 wt%), rare-earth metals (La 28.62 wt%), and noble metals (Ag 27.04 wt%). The strong oxalic acid-metal chelation and concurrent entangled polymer networks enable high-loading SACs. High-density single atoms induce site-intensive effects, modulating electron density and valence states to achieve peroxymonosulfate-based Fenton-like reactions with rate constants 1-2 orders of magnitude higher than conventional SACs. Elevated metal loading boosts Fenton-like potential jumps, facilitates electron transfer, and reduces the rate-limiting energy barrier in 1O2 production. This material is also proven effective in real wastewater treatment, combining high decontamination efficiency with operational stability. It is anticipated that the cascade-anchoring synthesis strategy will take SACs a step closer to practical applications. Single-atom catalysts typically suffer from low metal-loading limitations. Here, authors develop a universal method for achieving record loadings via chelation-polymer networks. These high-density catalysts exhibit enhanced electron modulation and catalytic activity.

Single-atom photocatalysts can modulate the utilization of photons and facilitate the migration of photogenerated carriers. However, the preparation of single-atom uniformly doped photocatalysts is still a challenging topic. Herein, we propose the preparation of Ni single-atom doped g-C3N4 photocatalysts by metal vapor exfoliation. The Ni vapor produced by calcining nickel foam at high temperature accumulates in between g-C3N4 layers and poses a certain vapor pressure to destroy the interlayer van der Waals forces of g-C3N4. Individual metal atoms are doped into the structure while exfoliating g-C3N4 into nanosheets by metal vapor. Upon optimization of Ni content, the Ni single atom doped g-C3N4 nanosheets with 2.81 wt% Ni exhibits the highest CO2 reduction performance in the absence of sacrificial agents. The generation rates of CO and CH4 are 19.85 and 1.73 μmol g-1h-1, respectively. The improved photocatalytic performance is attributed to the anchoring Ni of single atoms on g-C3N4 nanosheets, which increases both carrier separation efficiency and reaction sites. This work provides insight into the design of photocatalysts with highly dispersed single-atom.

Despite coordination environment of catalytic metal sites has been recognized to be of great importance in single-atom catalysts (SACs), a significant challenge remains in the understanding how the location-specific microenvironment in the higher coordination sphere influences their catalysis. Herein, a series of Cu-based SACs, namely Cu1/UiO-66-X (X = -NO2, -H, and -NH2), are successfully constructed by anchoring single Cu atoms onto the Zr-oxo clusters of metal-organic frameworks (MOFs), i.e. UiO-66-X. The -X functional groups dangling on the MOF linkers could be regarded as location-specific remote microenvironment to regulate electronic properties of the single Cu atoms. Remarkably, they exhibit significant differences in the catalysis toward the hydroboration of alkynes. The activity follows the order of Cu1/UiO-66-NO2 ˃ Cu1/UiO-66 ˃ Cu1/UiO-66-NH2 under identical reaction conditions, where Cu1/UiO-66-NO2 showcases the phenylacetylene conversion of 92%, ~3.5 times higher efficiency than that of Cu1/UiO-66-NH2. Experimental and calculation results jointly support that the Cu electronic structure is modulated by the location-specific microenvironment, thereby regulating the product desorption and promoting the catalysis.

As an easily tunable electrocatalytic substrate material, graphene is widely used in the hydrogen evolution reaction (HER) during water electrolysis. Research on this type of catalyst is still limited, and there is insufficient understanding of the impact of the nitrogen coordination environment. Our research explored the electronic construction and hydrogen evolution reaction effect of nitrogen-doped graphene anchored transition metal single atoms TM@Nx−G as single-atom catalysts using first-principle calculations, focusing on different nitrogen coordination structures. The results show that the powerful interplay between doped nitrogen atoms and transition metal atoms at the catalytic center endows the catalyst with enhanced catalytic activity and thermodynamic stability. Notably, the screened Ti@N3-G and Mn@N3-G exhibit good catalytic activity, outperforming the standard Pt catalyst. The catalytic performance and stability of the TM@Nx-G structures are influenced by the nitrogen coordination structural environment due to variations in the geometric and electronic structures. This work provides predictions and insights for the further development of carbon-based HER functional electrocatalysts.

Achieving high metal loadings in metal–organic frameworks (MOFs)‐based single‐atom catalysts (SACs) remains a major challenge due to the degradation of anchoring sites during high‐temperature synthesis. Here, a low‐temperature photochemical reduction strategy that preserves the structural integrity of MOF and maximizes the density of unsaturated pyridinic nitrogen sites for efficient metal atom anchoring is reported. This pyrolysis‐free approach enables the synthesis of SACs with record‐high metal loadings, up to 20.5 wt.% for Pt, 16.9 wt.% for Ru, 15.4 wt.% for Os, 12.9 wt.% for Fe, and 9.6 wt.% for Cu, surpassing previous MOF‐derived SACs by one order of magnitude. Density functional theory (DFT) calculations reveal that the unique Pt‐N2Cl2 coordination significantly enhances oxidase‐like activity compared to conventional Pt‐N3 configurations. Furthermore, the high metal loading increases the density of catalytically active sites, thereby improving overall catalytic efficiency. As a proof of concept, a Pt‐SACs@MOF‐based immunosensor achieves ultrasensitive detection of α‐fetoprotein (AFP) with a detection limit as low as 3 fg mL−1. This work offers a general and scalable strategy for synthesizing high‐density SACs, addressing the long‐standing trade‐off between metal loading and structural stability in MOF‐based catalysts.

No abstract available

Designing high‐performance and low‐cost electrocatalysts for oxygen evolution reaction (OER) is critical for the conversion and storage of sustainable energy technologies. Inspired by the biomineralization process, we utilized the phosphorylation sites of collagen molecules to combine with cobalt‐based mononuclear precursors at the molecular level and built a three‐dimensional (3D) porous hierarchical material through a bottom‐up biomimetic self‐assembly strategy to obtain single‐atom catalysts confined on carbonized biomimetic self‐assembled carriers (Co SACs/cBSC) after subsequent high‐temperature annealing. In this strategy, the biomolecule improved the anchoring efficiency of the metal precursor through precise functional groups; meanwhile, the binding‐then‐assembling strategy also effectively suppressed the nonspecific adsorption of metal ions, ultimately preventing atomic agglomeration and achieving strong electronic metal‐support interactions (EMSIs). Experimental characterizations confirm that binding forms between cobalt metal and carbonized self‐assembled substrate (Co–O4–P). Theoretical calculations disclose that the local environment changes significantly tailored the Co d‐band center, and optimized the binding energy of oxygenated intermediates and the energy barrier of oxygen release. As a result, the obtained Co SACs/cBSC catalyst can achieve remarkable OER activity and 24 h durability in 1 M KOH (η10 at 288 mV; Tafel slope of 44 mV dec−1), better than other transition metal‐based catalysts and commercial IrO2. Overall, we presented a self‐assembly strategy to prepare transition metal SACs with strong EMSIs, providing a new avenue for the preparation of efficient catalysts with fine atomic structures.

Bisphenol A (BPA), a common endocrine-disrupting chemical, poses serious threats to both ecological systems and human health even at trace concentrations. However, the accurate detection of BPA in complex matrices remains challenging due to the low sensitivity and poor selectivity of conventional electrochemical sensing platforms. The saturated N4-coordinated single-atom sites derived from metal phthalocyanines exhibit high catalytic specificity and atomic utilization efficiency, enabling selective recognition of BPA. These characteristics enhance adsorption and electron transfer processes, potentially overcoming the limitations of traditional sensing materials and offering a feasible route for the ultra-sensitive detection of trace BPA in complex environments. In this study, we have developed a highly efficient electrochemical sensor for BPA by anchoring saturated N4-coordinated single-atom sites of metal phthalocyanine onto carbon spheres (MPc/CSs, where M = Fe, Co, and Ni). The carbon spheres (CSs) serve as substrates to support the metal phthalocyanine molecules, improving the stability of the active sites and preventing aggregation. Among the materials tested, FePc/CSs exhibited the highest sensitivity (0.53 μA μM-1) and the lowest limit of detection (0.031 μM), exhibiting better performance than other modified electrodes, including CoPc/CSs, NiPc/CSs, and metal-free phthalocyanine-loaded CSs (H2Pc/CSs). Structural analysis revealed that the Fe-N4 single-atom sites possess higher charge density than the Co-N4 and Ni-N4 single-atom sites, resulting in their superior catalytic activity. Practical validation of the FePc/CSs modified glassy carbon electrode (GCE) in real samples, such as supermarket receipts and plastic products, yielded satisfactory recovery rates (97.5-103.4 %), confirming the sensor's reliability in complex matrices. These results demonstrate that electrodes based on CSs-supported single-atom iron sites can serve as highly sensitive, selective, and cost-effective electrochemical sensors for BPA. Overall, this work provides an efficient strategy for designing high-performance environmental sensors based on engineered electronic microenvironments and offers valuable insights for the sensitive analysis of environmental pollutants.

Cocatalyst is of paramount significance to provide fruitful active sites for suppressing the spatial charge recombination toward boosted photocatalysis. Up to date, exploration of robust and stable cocatalysts is remained challenging. Inspired by the intrinsic merits of single-atom catalysts (SACs), such as distinctive electronic structure and high atomic utilization efficiency, single-atom/transition metal chalcogenides (TMCs) is utilized as a model to synthesize CdS-Pd single-atom catalyst (CdS-PdSA) heterostructures. This demonstrates the precise anchoring of isolated metal single-atom catalysts (SACs) onto TMCs through a simple yet effective wet-chemical strategy. The resulting heterostructures exhibit significantly enhanced and stable photocatalytic activity for selective anaerobic organic transformations and hydrogen production under visible light. This enhancement is primarily inferred due to the role of Pd SACs as electron pumps, which directionally trap the electrons photoexcited over CdS, accelerating the spatial charge separation and prolonging the carrier lifespan. The charge transport route and photocatalytic mechanism are elucidated. This work underscores the potential of SACs as cocatalysts in heterogeneous photocatalysis, offering valuable insights for the rational design of atomic-level cocatalysts for solar-to-chemical energy conversion and beyond.

The direct hydrogenation of 2-nitroacylbenzene to 2,1-benzisoxazole presents a significant challenge in the pharmaceutical and fine chemicals industries. In this study, a defect engineering strategy is employed to create bifunctional single-atom catalysts (SACs) by anchoring Pt single atoms onto metal vacancies within MgO(Al) nanosheets. The resultant Pt1/MgO(Al) SAC displays an exceptional catalytic activity and selectivity in the hydrogenation-cyclization of 2-nitroacylbenzene, achieving a 97.5% yield at complete conversion and a record-breaking turnover frequency of 458.8 h-1 under the mild conditions. The synergistic catalysis between the fully exposed single-atom Pt sites within a unique Pt-O-Mg/Al moiety and the abundant basic sites of the MgO(Al) support is responsible for this outstanding catalytic performance. The current work, therefore, paves the way for developing bifunctional or multifunctional SACs that can enhance efficient organocatalytic conversions.

Porphyrin-linked graphdiyne (PGDY) is a carbon-based material provides a platform for anchoring single-atom catalysts (SACs) with transition metals (TM). These SACs have the potential to boost the catalytic activity of...

In the field of electrocatalysis, single-atomic-layer tungsten, copper, and cobalt oxide on CeO2, ethylene diamine (ED) and reduced graphene oxide (rGO) supported materials shows tremendous potential. Despite the enormous interest in single metal atom oxide (SMAO) catalysts, it is still very difficult to directly convert readily available bulk metal oxide into single atom oxide. It is crucial and tough to create high performance materials for the oxygen evolution reaction (OER) in an alkaline environment. Herein, a single tungsten, copper and cobalt atom oxide (SMAO) anchored on the CeO2 atomic layer and overall components deposited on the rGO (rGO-ED-CeO2-WCuCo) is prepared through a one-pot sonication technique. The presence of SMAO is identified by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging. The electrocatalytic performance of final rGO-ED-CeO2-WCuCo-30 nanocomposite for the OER in 1 M KOH electrolyte is evidenced by providing low overpotential of 283 mV at 10 mA cm-2. The Tafel slope for OER using rGO-ED-CeO2-WCuCo-30 electrocatalysts is 57.03 mV dec-1. The electrocatalytic activity of rGO-ED-CeO2-WCuCo-30 nanocomposites for OER was noticeably increased when compared to bare CeO2 nanorods (401 mV), rGO-ED-CeO2-WCo-30 (345 mV), rGO-ED-CeO2-WCu-30 (340 mV) and rGO-ED-CeO2-WCuCo-20 (321 mV) samples.

Designing new synthesis routes to fabricate highly thermally durable precious metal single-atom catalysts (SACs) is challenging in industrial applications. Herein, a general strategy is presented that starts from dual-metal nanocrystals (NCs), using bimetallic NCs as a facilitator to spontaneously convert a series of noble metals to single atoms on aluminum oxide. The metal single atoms are captured by cation defects in situ formed on the surface of the inverse spinel (AB2O4) structure, which process provides numerous anchoring sites, thus facilitating generation of the isolated metal atoms that contributes to the extraordinary thermodynamic stability. The Pd1/AlCo2O4-Al2O3 shows not only improved low-temperature activity but also unprecedented (hydro)thermal stability for CO and propane oxidation under harsh aging conditions. Furthermore, our strategy exhibits a small scaling-up effect by the simple physical mixing of commercial metal oxide aggregates with Al2O3. The good regeneration between oxidative and reductive atmospheres of these ionic palladium species makes this catalyst system of potential interest for emissions control.

The rational design of catalytic host materials with optimized electronic structures and confined architectures is crucial for addressing the shuttle effect and sluggish kinetics in aqueous zinc‐iodine batteries. In this study, an asymmetric cobalt single‐atom catalyst is developed by anchoring Co−N3P1 sites on a nitrogen‐phosphorus co‐doped carbon matrix (Co−N−PC) derived from metal–organic frameworks (MOFs). The coordination engineering of Co centers via phosphorus incorporation disrupts the symmetry of conventional Co−N4 configurations, enhancing charge redistribution and reducing the energy barrier for iodine dissociation as confirmed by density functional theory calculations. Systematic optimization reveals that moderate Co and P doping balances active sites and electronic conductivity, achieving strong chemical adsorption of polyiodides while maintaining structural stability. In situ Raman and UV–Vis spectroscopies confirm effective confinement of iodine species and reversible iodine conversion. The optimized C3/I2 cathode exhibits exceptional cyclability, retaining a specific capacity of 100.6 mA h g−1 after 50,000 cycles at 5 A g−1. Furthermore, practical applicability is demonstrated in flexible soft‐pack batteries and 3D‐printed/screen‐printed micro‐batteries, showing its potential for scalable energy storage. This work presents a heteroatom‐modulation strategy for designing efficient catalytic hosts in conversion‐type batteries.

Single-atom Fenton-like catalysts supported on graphitic carbon nitride (g-C3N4) show great potential for aqueous organic pollutant degradation but are hindered by structural heterogeneity and inefficient metal anchoring. Herein, a precise synthesis strategy that can balance metal precursor supply and anchoring site formation is proposed to construct iron single-atom catalysts (Fe-SACs) on a g-C3N4/montmorillonite (MMT) heterostructure. Directional electron transfer from MMT to g-C3N4 was found to strengthen metal-support interactions, optimizing interfacial electron redistribution and significantly enhancing both catalytic activity and stability. The optimized FNC-MMT (Fe@C3N4-MMT) SACs system achieved >95 % pollutant degradation efficiency over 2000 min in continuous flow operation, with a kinetic rate constant (k = 1.4404 min-1) 36-, 758-, and 2880-fold higher than Fe- C3N4 SACs, pristine g- C3N4, and individual MMT, respectively. Under visible light, the heterostructure exhibited exceptional photocatalytic cycling performance, confirming the critical role of interfacial electron synergy. Mechanistic studies revealed that the system activates peroxymonosulfate (PMS) via a non-radical pathway dominated by 1O2 generation and direct electron transfer, as evidenced by in situ Electron spin resonance (ESR) and electrochemical analysis like Galvanic oxidation process. DFT calculations further demonstrated that MMT optimizes the electronic structure of Fe sites, lowering the energy barrier for PMS activation. This work provides a scalable approach for synthesizing stable SACs as well as fundamental insights into electronic-structure-mediated non-radical catalysis, advancing the design of high-efficiency systems for water purification.

Heterogeneous single-atom catalysts (SACs) have gained significant attention for their maximized atom utilization and well-defined active sites, but they often struggle with multi-stage organic cross-coupling reactions due to limited coordination space and reactivity. Here, we report an “anchoring-borrowing” strategy combined facet engineering to develop artful single-atom catalysts (ASACs) through anchoring foreign single atoms onto specific facets of the non-innocent reducible carriers. ASACs exhibit adaptive coordination, effectively bypassing the oxidative-addition prerequisite for bivalent elevation at a single metal site in both homogenous and heterogeneous cross-couplings. For example, Pd1-CeO2(110) ASAC exhibits unparalleled activity in coupling with more accessible aryl chlorides, and challenging heterocycles, outperforming traditional catalysts with a remarkable turnover number of 45,327,037. Mechanistic studies reveal that ASACs leverage dynamic structural changes, with reducible carriers acting as electron reservoirs, significantly lowering reaction barriers. Furthermore, ASACs enable efficient synthesis of biologically significant compounds, drug intermediates, and active pharmaceutical ingredients (APIs) through a scalable high-speed circulated flow synthesis, underscoring great potential for sustainable fine chemical manufacturing. Heterogeneous single-atom catalysts (SACs) offer high atom utilization and well-defined active sites but face challenges in multi-stage cross-couplings due to limited coordination and reactivity. Here, the authors introduce SACs on reducible carriers, enabling adaptive coordination to bypass oxidative addition in cross-couplings.

MXene based sulfur hosts have attracted enormous attention in room temperature sodium-sulfur (RT Na-S) batteries due to their strong affinity towards soluble sodium polysulfides (NaPSs). However, their electrocatalytic performance needs further improvement. Here, a series of single non-noble transition metal (TM = Fe, Co, Ni, and Cu) atoms anchored on Ti2CS2 (TM@Ti2CS2) were proposed as bifunctional sulfur hosts for Na-S batteries. The results testify that the introduction of TMs dramatically enhanced the chemical interaction between sulfur-containing species and Ti2CS2, which is attributed to the co-formation of TM-S and Na-S covalent bonds. Importantly, compared with pristine Ti2CS2, the sulfur reduction reaction (SRR) is thermodynamically more favorable on TM@Ti2CS2. In addition, the incorporation of Fe, Co, and Ni atoms is also conducive to promoting the dissociation of Na2S. The density of states (DOS) results suggest that TM@Ti2CS2 maintains metallic conductivity during the whole charge and discharge process. Overall, constructing single atom catalysts is an effective strategy to further improve the electrochemical performance of MXene based sulfur hosts for Na-S batteries.

Nonprecious transition metal catalysts have emerged as the preferred choice for industrial alkaline water electrolysis due to their cost-effectiveness. However, their overstrong binding energy to adsorbed OH often results in the blockage of active sites, particularly in the cathodic hydrogen evolution reaction. Herein, we found that single-atom sites exhibit a puncture effect to effectively alleviate OH blockades, thereby significantly enhancing the alkaline hydrogen evolution reaction (HER) performance. Typically, after anchoring single Ru atoms onto tungsten carbides, the overpotential at 10 mA·cm-2 is reduced by more than 130 mV (159 vs 21 mV). Also, the mass activity is increased 16-fold over commercial Pt/C (MA100 = 17.3 A·mgRu-1 vs 1.1 A·mgPt-1, Pt/C). More importantly, such electrocatalyst-based alkaline anion-exchange membrane water electrolyzers can exhibit an ultralow potential (1.79 Vcell) and high stability at an industrial current density of 1.0 A·cm-2. Density functional theory (DFT) calculations reveal that the isolated Ru sites could weaken the surrounding local OH binding energy, thus puncturing OH blockage and constructing bifunctional interfaces between Ru atoms and the support to accelerate water dissociation. Our findings exhibit generality to other transition metal catalysts (such as Mo) and contribute to the advancement of industrial-scale alkaline water electrolysis.

The rational design of high-performance catalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is essential for the development of clean and renewable energy technologies, particularly in fuel cells and metal-air batteries. Two-dimensional (2D) covalent organic frameworks (COFs) possess numerous hollow sites, which contribute to the stable anchoring of transition metal (TM) atoms and become promising supports for single atom catalysts (SACs). Herein, the OER and ORR catalytic performance of a series of SACs based on TQBQ-COFs were systematically investigated through density functional theory (DFT) calculations, with particular emphasis on the role of the coordination environment in modulating catalytic activity. The results reveal that Rh/TQBQ exhibits the most effective OER catalytic performance, with an overpotential of 0.34 V, while Au/TQBQ demonstrates superior ORR catalytic performance with an overpotential of 0.50 V. A critical mechanistic insight lies in the distinct role of boundary oxygen atoms in TQBQ, which perturb the adsorption energetics of reaction intermediates, thereby circumventing conventional scaling relationships governing OER and ORR pathways. Furthermore, we established the adsorption energy of TM atoms (Ead) as a robust descriptor for predicting catalytic activity, enabling a streamlined screening strategy for SAC design. This study emphasizes the significance of the coordination environment in determining the performance of catalysts and offers a new perspective on the design of novel and effective OER/ORR COFs-based SACs.

Anchoring single metal atoms on enzymes has great potential to generate hybrid catalysts with high activity and selectivity for reactions that cannot be driven by traditional metal catalysts. Herein, we develop a photochemical method to construct a stable single-atom enzyme-metal complex by binding single metal atoms to the carbon radicals generated on an enzyme-polymer conjugate. The metal mass loading of Pd-anchored enzyme is up to 4.0% while maintaining the atomic dispersion of Pd. The cooperative catalysis between lipase-active site and single Pd atom accelerates alkyl-alkyl cross-coupling reaction between 1-bromohexane and B-n-hexyl-9-BBN with high efficiency (TOF is 540 h−1), exceeding that of the traditional catalyst Pd(OAc)2 by a factor of 300 under ambient conditions. Single atom catalysts have been described for efficient and selective metal catalysis, while enzymes have been known for their recognition and binding. In this manuscript, the authors develop a photochemical method to combine the two platforms in one, and demonstrate it by anchoring Pd atoms on Candida Antarctic lipase B, for highly efficient alkyl-alkyl cross-coupling reactions.

A piezoelectric polymer membrane based on single metal atoms was demonstrated to be effective by anchoring isolated calcium (Ca) atoms on a composite of nitrogen-doped carbon and polyvinylidene fluoride (PVDF). The addition of Ca-atom-anchored carbon nanoparticles not only promotes the formation of the β phase (from 29.8 to 56.3%), the most piezoelectrically active phase, in PVDF, but also introduces much higher porosity and hydrophilicity. Under ultrasonic excitation, the fabricated catalyst membrane demonstrates a record-high and stable dye decomposing rate of 0.11 min-1 and antibacterial efficiencies of 99.8%. Density functional theory calculations reveal that the primary contribution to catalytic activity arises from single-atom Ca doping and that a possible synergistic effect between PVDF and Ca atoms can improve the catalytic performance. It is shown that O2 molecules can be easily hydrogenated to produce ·OH on Ca-PVDF, and the local electric field provided by the β-phase-PVDF might enhance the production of ·O2-. The proposed polymer membrane is expected to inspire the rational design of piezocatalysts and pave the way for the application of piezocatalysis technology for practical environmental remediation.

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Developing Pt-based core-shell catalysts with ultralow Pt loading, superior performance, and extended durability holds tremendous potential for advancing electrochemical energy storage and conversion technologies. However, current synthetic limitations persist in achieving atomically efficient Pt monolayer deposition on nonprecious metal substrates, hindering the maximization of Pt atomic utilization for cost-effective catalyst design. Here, we demonstrate a galvanic replacement strategy to synthesize tensile-strained platinum single-atom-layer (Pt SAL) on α-MoC substrates. The Pt SAL catalysts enable cooperative catalysis between adjacent Pt sites while maintaining nearly 100% atomic utilization efficiency. For alkaline hydrogen evolution, the Pt SAL/α-MoC catalyst exhibits optimized reaction energetics, reducing activation barriers for water dissociation, hydrogen adsorption, and H2 desorption compared to typical Pt/C. As a result, the Pt SAL catalysts exhibit superior hydrogen evolution reaction (HER) performance, with a mass activity of 1.71 A mgPt-1 at an overpotential of 50 mV, surpassing commercial Pt/C by 6.35-fold and single-atom catalysts by 7.68-fold. Remarkably, the Pt SAL catalysts reveal negligible activity decay after 10,000 cycles, with density functional theory (DFT) calculations attributing this stability to strong Pt-Mo interfacial bonding. In situ Raman spectroscopic studies reveal dynamic interfacial water restructuring that accelerates reaction kinetics. This work establishes a versatile synthesis approach for noble metal SAL catalysts and explores their role in designing high-performance electrocatalysts for heterogeneous catalysis.

Construction and optimization of stable atomically dispersed metal sites on SiO2 surfaces are important yet challenging topics. In this work, we developed the amino group-assisted atomic layer deposition strategy to deposit the atomically dispersed Pt on SiO2 support for the first time, in which the particle size and ratio of Pt entities from single atom (Pt1) to atomic cluster (Ptn) and nanoparticle (Ptp) on the SiO2 surface were well modulated. We demonstrated the importance of dual-site synergy for optimizing the activity of single-atom catalysts. The Pt1+n/SiO2–N catalysts with the coexistence of Pt1 and Ptn showed excellent activity and optimized selectivity (99% for haloanilines) in halonitrobenzenes hydrogenation, while Pt1/SiO2–N catalysts were almost inactive in the reaction. Mechanism investigation indicates that the Ptn site is beneficial for H2 dissociation, and the Pt1 site is energetically favorable for adsorption of the nitro group to complete the selective hydrogenation, which synergistically contributes to the optimized catalytic performances. This study provides a new strategy for constructing atomically dispersed metal species over the SiO2 support and demonstrates the significance of the synergy of dual active sites for enhancing the catalytic efficiency.

Single-atom catalysts (SACs) hold great promise in highly sensitive and selective gas sensors due to their ultrahigh atomic efficiency and excellent catalytic activity. However, due to the extremely high surface energy of SACs, it is still a huge challenge to synthesize a stable single-atom metal on sensitive materials. Here, we report an atomic layer deposition (ALD) strategy for the elaborate synthesis of single-atom Pt on oxygen vacancy-rich Fe2O3 nanosheets (Pt-Fe2O3-Vo), which displayed ultrafast and sensitive detection to H2, achieving the stability of Pt single atoms. Gas-sensing investigation showed that the Pt-Fe2O3-Vo materials enabled a significantly enhanced response of 26.5-50 ppm of H2, which was 17-fold higher than that of pure Fe2O3, as well as ultrafast response time (2 s), extremely low detection limit (86 ppb), and improved stability. The experimental and density functional theory (DFT) studies revealed that the abundant oxygen vacancy sites of Fe2O3 contributed to stabilizing the Pt atoms via electron transfer. In addition, the stabilized Pt atoms also greatly promote the electron transfer of H2 molecules to Fe2O3, thereby achieving an excellent H2 sensing performance. This work provides a potential strategy for the development of highly selective and stable chemical sensors.

Size-dependent catalysis is a classic and yet challenging issue in heterocatalysis because it is influenced by multiple factors such as varied metal loading and potential support effects. To the best of our knowledge, size-dependent catalytic research under the same metal loadings has rarely been reported. Herein, we designed and synthesized a series of unreducible SiO2-supported Pt-based catalysts with the same metal loadings (0.3 wt %) but different particle sizes from single atom (SA), cluster to nanoparticle by combining amino group-assisted atomic layer deposition with the designed activation strategy. Their catalytic properties were probed in the archetypal CO oxidation reaction. The catalytic activity boosts prominently with increased particle size, which is well consistent with the directly observed gradual aggregation-activation process during the reaction process tracked by in situ STEM and isotope-labeled surface reaction and rationalized by theoretical calculations. The dynamic size transform and surface-confinement effect of porous SiO2 also enable the Pt catalysts to achieve ultrahigh durability (> 2160 h) under the complete oxidation of CO, which is predominantly catalyzed by Pt nanoclusters/nanoparticles through the combined Mars-van Krevelen (66%) and Langmuir-Hinshelwood (34%) mechanisms. Similar phenomena were also found in catalytic hydrogenation and H2O2-involved oxidation reactions, i.e., SAs were poorly active, and nanoclusters/nanoparticles were clearly identified as the real active species. The dissociation energy of key small molecules (H2/O2/H2O2) is correlated with the particle size and catalytic activity, which can potentially act as a descriptor for the reaction activity. The present findings will afford deeper insights for deciphering the nature of size-dependent catalysis.

The precise synthesis of single-atom Zr catalysts on ultrathin 2D MWW zeolites remains challenging due to inevitable Zr clustering, expensive precursors, and complex post-treatments. Here, an alcohol-assisted salt-spreading deposition (ASD) strategy is reported to immobilize atomically dispersed Zr sites on pre-synthesized single-layer MWW nanosheets (SL-MWW). Derive benefit from the abundant external silanol groups (SiOHext) on the external surface of ultrathin 2D-MWW, tetracoordinated Zr─O4 configurations are grafted via a facile ASD process without toxic organic solvents. Characterizations including HAADF-STEM and XAS confirm the atomic dispersion and unique tetracoordinated structure of the Zr site. The resulting Zr-SL(ASD) catalyst exhibits exceptional Lewis acidity and accessibility, achieving superior selectivity and high conversion in Meerwein-Ponndorf-Verley reduction and etherification (MPV-ETH) cascade reaction of α, β-unsaturated carbonyl compounds and transesterification to valorized biomass under mild conditions. Comparative studies reveal three possible interaction pathways between external silanol groups and Zr species that govern atomic dispersion. The ASD approach successfully eliminates expensive and toxic organometallic precursors or energy-intensive treatments, offering a green and scalable route to prepare single-atom Zr-MWW catalysts. This work provides new insights into designing efficient and sustainable zeolite-based catalysts for biomass valorization.

Single-atom catalysts (SACs) can achieve excellent catalytic efficiency at ultralow catalyst consumptions. Herein, platinum (Pt) atoms are fixed on the wall of atomic layer deposition (ALD)-made molybdenum disulfide nanotube arrays (MoS2 -NTA) for efficient hydrogen evolution reaction (HER). More concretely, MoS2 -NTA with different nanotube diameters and wall thicknesses are fabricated by a sacrificial strategy of anodic aluminum oxide (AAO) template via ALD; then Pt atoms are fixed on the wall of Ti3 C2 -supported MoS2 -NTA as a catalytic system. The MoS2 -NTA/Ti3 C2 decorated with 0.13 wt.% of Pt results in a low overpotential of 32 mV to deliver a current density of 10 mA cm-2 , which is superior to 20 wt.% commercial Pt/C (41 mV). Ordered MoS2 -NTA instead of 2D MoS2 prevents Pt atoms from aggregating and then exerts catalytic activities. The density functional theory calculations suggest that the Pt atoms are more likely to occupy the sites on the tubular MoS2 than the planar MoS2 , and the Pt atoms accumulated at the Mo site of MoS2 -NT have a moderate Gibbs free energy (close to zero).

In the energy transition context, the design and synthesis of high‐performance Pt‐based photocatalysts with low Pt content and ultrahigh atom‐utilization efficiency for hydrogen production are essential. Herein, a facile approach for decorating atomically dispersed Pt cocatalysts having single‐atom (SA) and atomic cluster (C) dual active sites on CdS nanorods (PtSA+C/CdS) via atomic layer deposition is reported. The size of the cocatalyst and the spatial intimacy of the cocatalyst active sites are precisely engineered at the atomic scale. The PtSA+C/CdS photocatalysts show the optimized photocatalytic hydrogen evolution activity, achieving a reaction rate of 80.4 mmol h−1 g−1, which is 1.6‐ and 7.3‐fold higher than those of the PtSA/CdS and PtNP/CdS photocatalysts, respectively. Thorough characterization and theoretical calculations reveal that the enhanced photocatalytic activity is due to a remarkable synergy between SAs and atomic clusters as dual active sites, which are responsible for water adsorption–dissociation and hydrogen desorption, respectively. A similar synergetic effect is found in a representative Pt/TiO2 system, indicating the generality of the strategy. This study demonstrates the significance of the synergy between active sites for enhancing the reaction efficiency, opening a new avenue for the rational design of atomically dispersed photocatalysts with high efficiency.

Atomically dispersed heterometal catalysts offer ultrahigh atomic utilization and defined heterointerfaces for superior catalytic performance compared to single-metal-site analogues, yet their precise atomic-level construction remains challenging. Herein, a structure-defined atomic-cluster catalyst (PtSANiC/CNT) is synthesized via sequential atomic layer deposition (ALD). This strategy enables atomic-scale engineering of Pt surface exposure and electronic properties through controlled ALD cycles. The optimized PtSANiC/CNT exhibits exceptional activity and durability for ammonia borane (AB) hydrolytic dehydrogenation, breaking the activity-stability trade-off with 9.6-fold and 1.4-fold higher activity than PtSA/CNT (single-atom) and PtSANiSA/CNT (dual-atom) catalysts, respectively. Through in situ X-ray absorption spectroscopy, kinetic and dynamic analysis, and DFT calculations, we elucidate that PtSANiC interfacial sites synergistically promote concurrent H2O adsorption-dissociation and H2 desorption. Mechanistic studies reveal that nickel clusters facilitate H2O activation while Pt single atoms favor B-H bond cleavage due to an upshifted d-band center. This interfacial synergy also enhances selective hydrogenation and O2/H2O2-involved oxidation. The ALD-based atomic engineering approach provides a generalizable route to construct efficient and durable heterometal catalysts with defined active sites.

Single-atom catalysts (SACs) have attracted significant attention due to their superior catalytic activity and selectivity. However, the nature of active sites of SACs under realistic reaction conditions is ambiguous. In this work, high loading Pt single atoms on graphitic carbon nitride (g-C3 N4 )-derived N-doped carbon nanosheets (Pt1 /NCNS) is achieved through atomic layer deposition. Operando X-ray absorption spectroscopy (XAS) is performed on Pt single atoms and nanoparticles (NPs) in both the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR). The operando results indicate that the total unoccupied density of states of Pt 5d orbitals of Pt1 atoms is higher than that of Pt NPs under HER condition, and that a stable Pt oxide is formed during ORR on Pt1 /NCNS, which may suppress the adsorption and activation of O2 . This work unveils the nature of Pt single atoms under realistic HER and ORR conditions, providing a deeper understanding for designing advanced SACs.

Platinum-based catalysts have been considered the most effective electrocatalysts for the hydrogen evolution reaction in water splitting. However, platinum utilization in these electrocatalysts is extremely low, as the active sites are only located on the surface of the catalyst particles. Downsizing catalyst nanoparticles to single atoms is highly desirable to maximize their efficiency by utilizing nearly all platinum atoms. Here we report on a practical synthesis method to produce isolated single platinum atoms and clusters using the atomic layer deposition technique. The single platinum atom catalysts are investigated for the hydrogen evolution reaction, where they exhibit significantly enhanced catalytic activity (up to 37 times) and high stability in comparison with the state-of-the-art commercial platinum/carbon catalysts. The X-ray absorption fine structure and density functional theory analyses indicate that the partially unoccupied density of states of the platinum atoms’ 5d orbitals on the nitrogen-doped graphene are responsible for the excellent performance. Downsizing platinum based nanocatalysts has the twin advantages of lower platinum usage and increased activity per platinum atom. Here, the authors report an atomic layer deposition technique for single platinum atom catalyst fabrication and assess their hydrogen evolution activity.

Lithium metal electrodes have shown great promise for high capacity and the lowest potential. However, wide application is restricted by uncontrollable plating/stripping lithium behaviors, an uneven solid electrolyte interphase, and a lithium dendrite. Herein, the highly active single metal atom anchored in vacant catalyst is synthesized on the hierarchical porous nanocarbon (SACo/ADFS@HPSC). Acting as an artificial protective modulation layer on the lithium surface, the numerous atomic sites show the superiority in modulating lithium ion behaviors and smoothing the lithium surface without dendrite growth. As a consequence, the SACo/ADFS@HPSC-modified Li electrode lowers nucleation barrier (15 mV), extends the smooth plating lifespan (1600 h), and improves Coulombic efficiency, significantly accelerating the horizonal deposition of plated lithium. Coupled with a sulfur cathode, the fabricated pouch cell with 5.4 mg cm-2 delivers a high capacity of 3.78 mA h cm-2 corresponding to 1505 Wh kg-1, showing the promising practical application.

Configuring metal single-atom catalysts (SACs) with high electrocatalytic activity and stability is one efficient strategy in achieving the cost-competitive catalyst for fuel cells' applications. Herein, the atomic layer deposition (ALD) strategy for synthesis of Pt SACs on the metal-organic framework (MOF)-derived N-doped carbon (NC) is proposed. Through adjusting the ALD exposure time of the Pt precursor, the size-controlled Pt catalysts, from Pt single atoms to subclusters and nanoparticles, are prepared on MOF-NC support. X-ray absorption fine structure spectra determine the increased electron vacancy in Pt SACs and indicate the Pt-N coordination in the as-prepared Pt SACs. Benefiting from the low-coordination environment and anchoring interaction between Pt atoms and nitrogen-doping sites from MOF-NC support, the Pt SACs deliver an enhanced activity and stability with 6.5 times higher mass activity than that of Pt nanoparticle catalysts in boosting the oxygen reduction reaction (ORR). Density functional theory calculations indicate that Pt single atoms prefer to be anchored by the pyridinic N-doped carbon sites. Importantly, it is revealed that the electronic structure of Pt SAs can be adjusted by adsorption of hydroxyl and oxygen, which greatly lowers free energy change for the rate-determining step and enhances the activity of Pt SACs toward the ORR.

Single atom catalysts exhibit particularly high catalytic activities in contrast to regular nanomaterial-based catalysts. Until recently, research has been mostly focused on single atom catalysts, and it remains a great challenge to synthesize bimetallic dimer structures. Herein, we successfully prepare high-quality one-to-one A-B bimetallic dimer structures (Pt-Ru dimers) through an atomic layer deposition (ALD) process. The Pt-Ru dimers show much higher hydrogen evolution activity (more than 50 times) and excellent stability compared to commercial Pt/C catalysts. X-ray absorption spectroscopy indicates that the Pt-Ru dimers structure model contains one Pt-Ru bonding configuration. First principle calculations reveal that the Pt-Ru dimer generates a synergy effect by modulating the electronic structure, which results in the enhanced hydrogen evolution activity. This work paves the way for the rational design of bimetallic dimers with good activity and stability, which have a great potential to be applied in various catalytic reactions. Atomically precise control over elemental distributions presents a challenge in the preparation of catalytic nanomaterials. Here the authors report Pt-Ru bimetallic dimer structures through atomic layer deposition process and identify the roles of Pt and Ru in hydrogen evolution reaction.

Conversion of straight-chain paraffin into aromatics is particularly attractive but extremely challenging in the oil refining industry. Constructing the Pt-supported catalysts with high aromatics selectivity is vital important. Here, we report a strategy to use the Fe modified KL zeolite to improve Pt atom utilization efficiency and anchor them inside KL zeolite channels via atomic layer deposition (ALD) technique. A combination of highly dispersed single-atom Pt and electron-rich Pt clusters are fabricated on KL zeolite through proper nucleation sites creation. The resulted catalyst (PtFe-1/KL) exhibits excellent performance for the n-heptane aromatization (90.1 % aromatics selectivity) with the apparent activation energies of 131 kJ/mol and much enhanced stability at relatively lower temperature (420 oC). Experimental analysis and density functional theory (DFT) calculation illuminate that the single-atom Pt might play a key role in the initial dehydrogenation of n-heptane to 1-heptene, and the superior stable Pt clusters encapsulated inside Fe-decorated KL zeolite channels accelerate the 1-heptene dehydrocyclization to aromatics. The synergetic interaction between Pt single-atom and clusters enable PtFe-1/KL catalyst to be one of the most effective n-heptane aromatization catalysts reported to date.

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Bimetallic single‐atom‐dimer (SAD) with unique electronic structures and adsorption properties presents exceptional catalytic performance owing to atomic‐level synergistic effects from direct bonding between different metal atoms. However, inherent characteristics of substrate present great challenges in their synthesis and mechanism investigation. Herein, a unique phosphorus modified atomic layer deposition (P‐ALD) strategy is designed to synthesize P‐anchored Pt–W dimers, overcoming substrate limitation (Pt1W1–P/C). Motivated introduction of atomic P site via ALD can effectively anchor one‐to‐one AB bimetallic dimer structure on various substrates, confirmed by X‐ray absorption spectroscopy (XAS). Density functional theory reveals an interatomic synergistic adsorption mechanism, with W as primary hydrogen adsorption site extending to Pt, optimizing hydrogen coverage, leading to 60‐fold increase in mass activity compared to commercial Pt/C in both acidic and alkaline electrolytes. Anion exchange membrane water electrolyzer with ultra‐low loading Pt1W1–P/C (50 µgPt cm−2) catalyst operates durability at 1000 mA cm−2 for 550 h with ultra‐low degradation of 38 µV h−1. Operando XAS confirms hydrogen adsorption pathway between atoms and remarkable self‐healing ability of P–Pt–W–O sites under all‐pH conditions. These findings extend the application domain of SAD to catalytic manufacturing methods and aid in designing advanced materials with multi‐atomic active sites.

Applications of lithium–sulfur (Li–S) batteries are still limited by the sluggish conversion kinetics from polysulfide to Li2S. Although various single‐atom catalysts are available for improving the conversion kinetics, the sulfur redox kinetics for Li–S batteries is still not ultrafast. Herein, in this work, a catalyst with dual‐single‐atom Pt‐Co embedded in N‐doped carbon nanotubes (Pt&Co@NCNT) was proposed by the atomic layer deposition method to suppress the shuttle effect and synergistically improve the interconversion kinetics from polysulfides to Li2S. The X‐ray absorption near edge curves indicated the reversible conversion of Li2Sx on the S/Pt&Co@NCNT electrode. Meanwhile, density functional theory demonstrated that the Pt&Co@NCNT promoted the free energy of the phase transition of sulfur species and reduced the oxidative decomposition energy of Li2S. As a result, the batteries assembled with S/Pt&Co@NCNT electrodes exhibited a high capacity retention of 80% at 100 cycles at a current density of 1.3 mA cm−2 (S loading: 2.5 mg cm−2). More importantly, an excellent rate performance was achieved with a high capacity of 822.1 mAh g−1 at a high current density of 12.7 mA cm−2. This work opens a new direction to boost the sulfur redox kinetics for ultrafast Li–S batteries.

Single atom tailored metal nanoparticles represent a new type of catalysts. Herein, we demonstrate a single atom-cavity coupling strategy to regulate performance of single atom tailored nano-catalysts. Selective atomic layer deposition (ALD) was conducted to deposit Ru single atoms on the surface concavities of PtNi nanoparticles (Ru-ca-PtNi). Ru-ca-PtNi exhibits a record-high activity for methanol oxidation reaction (MOR) with 2.01 A mg -1 Pt . Also, Ru-ca-PtNi showcases a significant durability with only 16% activity loss. Operando electrochemical Fourier transform infrared spectroscopy (FTIR) and theoretical calculations demonstrate Ru single atoms coupled to cavities accelerate the CO removal by regulating d -band centre position. Further, the high diffusion barrier of Ru single atoms in concavities accounts for excellent stability. The developed Ru-ca-PtNi via single atom-cavity coupling opens an encouraging pathway to design highly efficient single atom-based (electro)catalysts.

Studies on single‐atom catalysts (SACs) with individually isolated metal atoms anchored on specific supports have gained great interest in photocatalysis due to their enhanced catalytic activity and optimal atom utilization. By providing an optimized number of active sites and enhancing their intrinsic activity, SACs afford a distinctive platform for photocatalysis at the atomic level. In this study, we investigate the photocatalytic H2 generation of Pt single atoms (SAs) anchored on CdS‐sensitized single crystalline anatase TiO2 nanoflakes (ATNF) in the visible spectral range. Vertically‐aligned ATNF were synthesized on fluorine‐doped tin oxide substrates by a hydrothermal process, which were further sensitized by CdS nanoislands (NIs) using the successive ionic layer adsorption and reaction (SILAR) technique. Finally, a reactive‐deposition approach was used to successfully anchor Pt SAs on CdS‐sensitized ATNF. Under optimized conditions, the highest photocatalytic H2 evolution on Pt‐anchored single atom CdS sensitized ATNF was 17.8 μL h−1 under visible light illumination, which is 15.8, 7.5, and 6.7‐fold higher than bare CdS/FTO, PtSA/CdS/FTO, and ATNF, respectively. Overall, the density of Pt SAs plays a vital role via strong trapping of the photogenerated electrons and significantly improves the efficiency of electron‐hole separation, making PtSA/ATNF efficient solar‐driven photocatalysts.

Single atomic Pt catalysts exhibit particularly high hydrogen evolution reaction (HER) activity compared to conventional nanomaterial-based catalysts. However, the enhanced mechanisms between Pt and their coordination environment are not understood in detail. Hence, a systematic study examining the different types of N in the support is essential to clearly demonstrate the relationship between Pt single atoms and N-doped support. Herein, three types of carbon nanotubes with varying types of N (pyridine-like N, pyrrole-like N, and quaternary N) are used as carbon support for Pt single atom atomic layer deposition. The detailed coordination environment of the Pt single atom catalyst is carefully studied by electron microscope and X-ray absorption spectra (XAS). Interestingly, with the increase of pyrrole-like N in the CNT support, the HER activity of the Pt catalyst also improves. First principle calculations results indicate that the interaction between the dyz and s orbitals of H and sp3 hybrid orbital of N should be the origin of the superior HER performance of these Pt single atom catalysts (SACs).

No abstract available

Single-atom catalysts have recently been subject to considerable attention within applied catalysis. However, complications in preparation of well-defined single-atom model systems have hampered efforts to determine the reaction mechanisms underpinning the reported activity. By means of an atomic layer deposition method utilizing the steric hindrance of the ligands, isolated Fe1O3 motifs were grown on a single-crystal Cu2O(100) surface at densities up to 0.21 sites per surface unit cell. Ambient pressure x-ray photoelectron spectroscopy shows a strong metal-support interaction with Fe in a chemical state close to 3+. Results from scanning tunneling microscopy and density functional calculations demonstrate that isolated Fe1O3 is exclusively formed and occupies a single site per surface unit cell, coordinating to two oxygen atoms from the Cu2O lattice and another through abstraction from O2. The isolated Fe1O3 motif is active for CO oxidation at 473 K. The growth method holds promise for extension to other catalytic systems.

Single-atom catalysis represents a new frontier that integrates the merits of homogeneous and heterogeneous catalysis to afford exceptional atom efficiency, activity, and selectivity for a range of catalytic systems. Herein we describe a simple defect engineering strategy to construct an atomically dispersed palladium catalyst (Pdδ+, 0 < δ < 2) by anchoring the palladium atoms on oxygen vacancies created in CeO2 nanorods. This was confirmed by spherical aberration correction electron microscopy and extended X-ray absorption fine structure measurement. The as-prepared catalyst showed exceptional catalytic performance in the hydrogenation of styrene (99% conversion, TOF of 2410 h-1), cinnamaldehyde (99% conversion, 99% selectivity, TOF of 968 h-1), as well as oxidation of triethoxysilane (99% conversion, 79 selectivity, TOF of 10 000 h-1). This single-atom palladium catalyst can be reused at least five times with negligible activity decay. The palladium atoms retained their dispersion on the support at the atomic level after thermal stability testing in Ar at 773 K. Most importantly, this synthetic method can be scaled up while maintaining catalytic performance. We anticipate that this method will expedite access to single-atom catalysts with high activity and excellent resistance to sintering, significantly impacting the performance of this class of catalysts.

No abstract available

Engineering the coordination environments and electronic structures of single-atom catalysts (SACs) to enhance their catalytic activity remains great challenge. Herein, we found that the reaction of precursors containing both nitrogen and oxygen atoms with Ni(II) under 500°C can generate a N/O mixing coordinated Ni-N3O SAC, in which the oxygen atom can be gradually removed under high temperature due to weaker Ni-O interaction, resulting in a vacancy-defect Ni-N3-V SAC at Ni site under 800°C. While the reaction of Ni(II) with the precursor simply containing nitrogen atoms can only obtain a none-vacancy-defect Ni-N4 SAC. Both the results of experimental and DFT calculations reveal that the presence of a vacancy-defect in Ni-N3-V SAC can dramatically boost the electrocatalytic activity for CO2 reduction, with extremely high CO2 reduction current density of 65 mA/cm2 and high Faradaic efficiency over 90% at -0.9 V vs RHE, as well as a record high turnover frequency of 1.35×105 h-1, much higher than those of Ni-N4 SAC, and being one of the best reported electrocatalysts for CO2-to-CO conversion to date.

The inherent trade-off between activity and stability in platinum single-atom catalysts (SACs) poses a significant challenge for catalytic oxidation reactions. High-coordination Pt sites have good stability, but their overoxidation often passivates activity. In contrast, metastable low-coordination Pt structures typically display high activity but are prone to oxidation and aggregation under harsh conditions. Herein, we propose a defect-engineering strategy to address this dilemma by anchoring oxidized Pt single atoms onto vacancy LaFeO3 (v-LaFeO3) perovskite. The introduced La-vacancy substantially reduces the oxygen vacancy formation energy of LaFeO3, enhancing lattice oxygen mobility while preserving structural integrity. Pt single-atom sites with a high oxidation state (Pt4+) are anchored on the support, and their coordination environments are optimized. The catalyst exhibits high and stable activity for CO oxidation without reduction pretreatment. The structural characterization and in situ experiments indicate that vacancies in LaFeO3 positively regulate the electronic structure between the Pt and v-LaFeO3 interface. The longer Pt-O bonds activate interface oxygen species, accelerate O2 activation, and promote the cycling of CO oxidation. The oxidized Pt atoms and high coordination number enable its stability in long-term and high-temperature oxidation reactions. DFT calculations further verify the structure and reaction mechanism. This work demonstrates that precise control of support defects can concurrently optimize the electronic states and stability of SACs, offering a generalized paradigm for designing robust oxidation catalysts.

Constructing single‐atom catalysts (SACs) and optimizing the electronic structure between metal atoms and support interactions is deemed one of the most effective strategies for boosting the catalytic kinetics of the hydrogen evolution reaction (HER). Herein, a sulfur vacancy defect trapping strategy is developed to anchor tungsten single atoms onto ultrathin V3S4 nanosheets with a high loading of 25.1 wt.%. The obtained W‐V3S4 catalyst exhibits a low overpotential of 54 mV at 10 mA cm−2 and excellent long‐term stability in alkaline electrolytes. Density functional theory calculations reveal that the in situ anchoring of W single atoms triggers the delocalization and redistribution of electron density, which effectively accelerates water dissociation and facilitates hydrogen adsorption/desorption, thus enhancing HER activity. This work provides valuable insights into understanding highly active single‐atom catalysts for large‐scale hydrogen production.

Carbon-defect engineering in single-atom metal-nitrogen-carbon (M─N─C) catalysts by straightforward and robust strategy, enhancing their catalytic activity for volatile organic compounds, and uncovering the carbon vacancy-catalytic activity relationship are meaningful but challenging. In this study, an iron-nitrogen-carbon (Fe─N─C) catalyst is intentionally designed through a carbon-thermal-diffusion strategy, exposing extensively the carbon-defective Fe─N4 sites within a micro-mesoporous carbon matrix. The optimization of Fe─N4 sites results in exceptional catalytic ozonation efficiency, surpassing that of intact Fe─N4 sites and commercial MnO2 by 10 and 312 times, respectively. Theoretical calculations and experimental data demonstrated that carbon-defect engineering induces selective cleavage of C─N bond neighboring the Fe─N4 motif. This induces an increase in non-uniform charges and Fermi density, leading to elevated energy levels at the center of Fe d-band. Compared to the intact atomic configuration, carbon-defective Fe─N4 site is more activated to strengthen the interaction with O3 and weaken the O─O bond, thereby reducing the barriers for highly active surface atomic oxygen (*O/*OO), ultimately achieving efficient oxidation of CH3 SH and its intermediates. This research not only offers a viable approach to enhance the catalytic ozonation activity of M─N─C but also advances the fundamental comprehension of how periphery carbon environment influences the characteristics and efficacy of M─N4 sites.

This study investigates the enhancement of catalytic activity in single-atom catalysts (SACs) through coordination engineering. By introducing non-metallic atoms (X = N, O, or F) into the basal plane of MoS2via defect engineering and subsequently anchoring hetero-metallic Ru atoms, we created 10 types of non-metal-coordinated Ru SACs (Ru–X–MoS2). Computations indicate that non-metal atom X significantly modifies the electronic structure of Ru, optimizing the hydrogen evolution reaction (HER). Across acidic, neutral, and alkaline electrolytes, Ru–X–MoS2 catalysts exhibit significantly improved HER performance compared with Ru–MoS2, even surpassing commercial Pt/C catalysts. Among these, the Ru–O–MoS2 catalyst, characterized by its asymmetrically coordinated O2–Ru–S1 active sites, demonstrates the most favorable electrocatalytic behavior and exceptional stability across all pH ranges. Consequently, single-atom coordination engineering presents a powerful strategy for enhancing SAC catalytic performance, with promising applications in various fields.

Carbon-defect engineering in metal single-atom catalysts by simple and robust strategy, boosting their catalytic activity, and revealing the carbon defect-catalytic activity relationship are meaningful but challenging. Herein, we report a facile self-carbon-thermal-reduction strategy for carbon-defect engineering of single Fe-N4 sites in ZnO-Carbon nano-reactor, as efficient catalyst in Fenton-like reaction for degradation of phenol. The carbon vacancies are easily constructed adjacent to single Fe-N4 sites during synthesis, facilitating the formation of C-O bonding and lowering the energy barrier of rate-determining-step during degradation of phenol. Consequently, the catalyst Fe-NCv-900 with carbon vacancies exhibits a much improved activity than the Fe-NC-900 without abundant carbon vacancies, with 13.5 times improvement in the first-order rate constant of phenol degradation. The Fe-NCv-900 shows high activity (97% removal ratio of phenol in only 5 min), good recyclability and the wide-ranging pH universality (pH range 3-9). This work not only provides a rational strategy for improving the Fenton-like activity of metal single-atom catalysts, but also deepens the fundamental understanding on how periphery carbon environment affects the property and performance of metal-N4 sites.

Atomically dispersed metal-nitrogen-carbon materials (AD-MNCs) are considered the most promising non-precious catalysts for the oxygen reduction reaction (ORR), but it remains a major challenge for simultaneously achieving high intrinsic activity, fast mass transport, and effective utilization of the active sites within a single catalyst. Here, an AD-MNCs consisting of defect-rich Fe-N3 sites dispersed with axially coordinated Te atoms on porous carbon frameworks (Fe1Te1-900) is designed. The local charge densities and energy band structures of the neighboring Fe and Te atoms in FeN3-Te are rearranged to facilitate the catalytic conversion of the O-intermediates. Meanwhile, the negative shift of the d-band center in FeN3-Te reduces the energy barrier limit for effective desorption of the final OH* intermediate. In the electrochemical evaluation, Fe1Te1-900 presents a more positive onset potential and half-wave potentials of 1.03 and 0.89 V versus the reversible hydrogen electrode, respectively. Furthermore, the liquid zinc-air batteries assembled with Fe1Te1-900 exhibited excellent performances compared to commercial Pt/C. This work opens up new ideas for the development of high-performance ORR electrocatalysts for applications in various energy conversion and storage technologies.

Electrochemical carbon dioxide reduction (ECO2RR) shows great potential to create high-value carbon-based chemicals, while designing advanced catalysts at the atomic level remains challenging. The ECO2RR performance is largely dependent on the catalyst microelectronic structure that can be effectively modulated through surface defect engineering. Here, we provide an atmosphere-assisted low-temperature calcination strategy to prepare a series of single-atomic Cu/ceria catalysts with varied oxygen vacancy concentrations for robust electrolytic reduction of CO2 to methane. The obtained Cu/ceria catalyst under H2 environment (Cu/ceria-H2) exhibits a methane Faraday efficiency (FECH4) of 70.03% with a turnover frequency (TOFCH4) of 9946.7 h-1 at an industrial-scale current density of 150 mA cm-2 in a flow cell. Detailed studies indicate the copious oxygen vacancies in the Cu/ceria-H2 are conducive to regulating the surface microelectronic structure with stabilized Cu+ active center. Furthermore, density functional theory calculations and operando ATR-SEIRAS demonstrate that the Cu/ceria-H2 can markedly enhance the activation of CO2, facilitate the adsorption of pivotal intermediates *COOH and *CO, thus ultimately enabling the high selectivity for CH4 production. This study presents deep insights into designing effective electrocatalysts for CO2 to CH4 conversion by controlling the surface microstructure via the reaction atmosphere.

Despite their great promise, the practical use of single-atom catalysts (SACs) is often limited by their unsatisfactory metal loading, primarily due to the limited availability of binding sites on the substrate. Herein, we report a defect-assisted metal trapping strategy to unlock the loading limit by generating highly tunable sulfur vacancies on ZnIn2S4 (ZIS) via electrochemical desulfurization, followed by the subsequent photodeposition of Co and Ni single atoms at high loadings (4.8 wt% Co and 6.7 wt% Ni). Such bimetallic SACs (Sv-ZIS-CoNi) exhibit a remarkable hydrogen evolution rate of 51.5 mmol g-1 h-1 under visible light due to synergistic interaction between adjacent Co and Ni atoms, outperforming state-of-the-art ZnIn2S4-based photocatalysts. Our catalyst retains 98% of its activity after five cycles of continuous operation due to the robust anchoring of single-atom sites at sulfur vacancies. This work provides a facile approach for synthesizing high-loading SACs through defect engineering.

No abstract available

Single-atom catalysts (SACs) feature maximum atomic utilization efficiency; however, the loading amount, dispersibility, synthesis cost, and regulation of the electronic structure are factors that need to be considered in water treatment. In this study, kaolinite, a natural layered clay mineral, is applied as the support for g-C3 N4 and single Fe atoms (FeSA-NGK). The FeSA-NGK composite exhibits an impressive degradation performance toward the target pollutant (>98% degradation rate in 10 min), and catalytic stability across consecutive runs (90% reactivity maintained after three runs in a fluidized-bed catalytic unit) under peroxymonosulfate (PMS)/visible light (Vis) synergetic system. The introduction of kaolinite promotes the loading amount of single Fe atoms (2.57 wt.%), which is a 14.2% increase compared to using a bare catalyst without kaolinite, and improved the concentration of N vacancies, thereby optimizing the regulation of the electronic structure of the single Fe atoms. It is discovered that the single Fe atoms successfully occupied five coordinated N atoms and combined with a neighboring N vacancy. Consequently, this regulated the local electronic structure of single Fe atoms, which drives the electrons of N atoms to accumulate on the Fe centers. This study opens an avenue for the design of clay-based SACs for water purification.

Single‐atom (SA) catalysis is a novel frontline in the catalysis field due to the often drastically enhanced specific activity and selectivity of many catalytic reactions. Here, an atomic‐scale defect engineering approach to form and control traps for platinum SA sites as co‐catalyst for photocatalytic H2 generation is described. Thin sputtered TiO2 layers are used as a model photocatalyst, and compared to the more frequently used (001) anatase sheets. To form stable SA platinum, the TiO2 layers are reduced in Ar/H2 under different conditions (leading to different but defined Ti3+‐Ov surface defects), followed by immersion in a dilute hexachloroplatinic acid solution. HAADF‐STEM results show that only on the thin‐film substrate can the density of SA sites be successfully controlled by the degree of reduction by annealing. An optimized SA‐Pt decoration can enhance the normalized photocatalytic activity of a TiO2 sputtered sample by 150 times in comparison to a conventional platinum‐nanoparticle‐decorated TiO2 surface. HAADF‐STEM, XPS, and EPR investigation jointly confirm the atomic nature of the decorated Pt on TiO2. Importantly, the density of the relevant surface exposed defect centers—thus the density of Pt‐SA sites, which play the key role in photocatalytic activity—can be precisely optimized.

Single atom nanozymes (SAEs), featuring atomically dispersed metallic active centers and maximum atomic utilization efficiency, have demonstrated outstanding catalytic activity compared with conventional nanozymes. The interaction between metallic active centers and carrier may play a crucial role for the improvement of catalytic performance of SAEs. In this work, we anchored an atomically dispersed Mn element on CuFe-layered double hydroxide with Mn content of 2.15 wt % through a defect engineering strategy, creating a synergistic dual-site catalyst denoted as Mn SAE. Owing to the interaction between the carrier and the metallic active centers, Mn SAE exhibited significantly enhanced superoxide dismutase- and catalase-mimicking activities. Additionally, it also demonstrated remarkable capability for scavenging hydroxyl radicals (•OH) and singlet oxygen (1O2). Thus, Mn SAE with synergistic antioxidant activity can be a powerful quenching agent for reactive oxygen species-mediated luminol-H2O2 chemiluminescence. By using it as a sensitive probe, we developed a chemiluminescent immunoassay method for fentanyl, with a linear range of 0.001-25 ng/mL and a detection limit of 0.3 pg/mL. Its practicability was successfully demonstrated by detecting fentanyl in diverse real samples. This investigation provides a new pathway for the development of synergistic dual-site SAEs with multiple antioxidant activities that are suitable for application in biosensing.

Atomic‐level tailoring of active sites is an efficient strategy for designing high‐performance photocatalysts for clean energy. Asymmetric atomic sites (AAS) like MSA‐Ov‐M2 created through hetero‐metal single atoms (MSA) doping on defect‐rich metal oxides (M2‐Ov‐M2) are favored for better activation of targeted molecules. However, creating AAS typically demands high energy input, hindering their widespread use in photocatalytic H2 production. Furthermore, precise control over surface defects to create AAS remains challenging. Here, CuSA‐Ov‐Ti3c highly asymmetric atomic sites catalyst (HAASC) is constructed by strategically trapping Cu single atoms on high‐index (111) faceted TiO2. This material combines single‐atom catalysis and facet engineering, achieving unprecedented H2 production rates (8.3 mmol h−1 g−1 in pure water and 784.5 mmol h−1 g−1 in water/methanol mixture). Experimental and theoretical analyses reveal CuSA substituting five‐coordinated Ti atoms (Ti5c) next to three‐coordinated (Ti3c) ones, forming CuSA‐Ov‐Ti3c HAAS. HAAS plays multiple roles in i) improving light harvesting, charge‐transfer dynamics, and redox capability of photoexcited electrons; ii) enhanced adsorption and polarization of H2O molecules; iii) facilitating electron transfer from CuSA‐Ov‐Ti3c to H2O molecules, and iv) raising d‐band center toward Fermi level resulting in ≈250‐fold enhanced H2 production than Ti5c‐O‐Ti3c AASC. This work opens new avenues for future structural designs in heterogeneous catalysis for energy‐related applications.

The oxygen reduction reaction (ORR) plays a fundamental role in sustainable energy technologies. However, the creation of non‐precious metal electrocatalysts with high ORR activity and durability under all pH conditions is of great significance but remains challenging. Herein, the aim is to overcome this challenge by creating a Fe single atom catalyst on a 2D defect‐containing nitrogen‐doped carbon support (Fe1/DNC) via a microenvironment engineering strategy. Microkinetic modeling reveals that FeN4(OH) moieties are the real active sites under reaction conditions. Due to the synergistic promotion effect of denser accessible FeN4(OH) moieties and defect‐induced electronic properties, Fe1/DNC catalyst achieves extraordinary ORR activity under alkaline, acidic, and neutral conditions, with half‐wave potentials of 0.95, 0.82, and 0.70 V, respectively. Moreover, a negligible performance decay is observed with this Fe catalyst in stability and methanol tolerance tests. Zn‐air battery employing Fe1/DNC delivers remarkable peak power density and long‐term operational durability. Theoretical analysis provides compelling evidence that the defects adjacent to FeN4(OH) moieties can endow an inductive effect to reshape electronic properties to balance the OOH* formation and OH* reduction. This work offers insight into the regulation of asymmetric coordination structure and electronic properties of metal sites for boosting electrocatalytic activity and stability.

Defect engineering in the inherently inert basal planes of transition metal dichalcogenides (TMDs), involving the introduction of chalcogen vacancies, represents a pivotal approach to enhance catalytic activity by exposing high-density catalytic metal single-atom sites. However, achieving a single-atom limit spacing between chalcogen vacancies to form ordered superstructures remains challenging for creating uniformly distributed high-density metal single-atom sites on TMDs comparable to carbon-supported single-atom catalysts (SACs). Here we unveil an efficient TMD-based topological catalyst for hydrogen evolution reaction (HER), featuring high-density single-atom reactive centers on a few-layer (7 × 7)-PtTe2-x superstructure. Compared with pristine Pt(111), PtTe2, and (2 × 2)-PtTe2-x, (7 × 7)-PtTe2-x exhibits superior HER performance owing to its substantially increased density of undercoordinated Pt sites, alongside exceptional catalytic stability when operating at high current densities. First-principles calculations confirm that multiple types of undercoordinated Pt sites on (7 × 7)-PtTe2-x exhibit favorable hydrogen adsorption Gibbs free energies, and remain active upon increasing hydrogen coverage. Furthermore, (7 × 7)-PtTe2-x possesses nontrivial band topologies with robust edge states, suggesting potential enhancements for HER. Our findings are expected to advance TMD-based catalysts and exploration of topological materials in catalysis.

Transition metal-nitrogen-carbon complexes, featuring single metal atoms embedded in a nitrogen-doped carbon matrix, emerge as promising alternatives to traditional platinum-based catalysts, offering cost-effectiveness, abundance, and enhanced catalytic performance. This work introduces a novel method for the etching and doping of zeolitic imidazolate frameworks (ZIFs) with transition metals, creating a uniform distribution of secondary metal centers on ZIF surfaces. By disrupting the crystalline symmetry of ZIFs through synthetic defect engineering, we gain access to their entire internal volume, creating multichannel pathways. The absorption of metal ions is theoretically simulated, demonstrating their thermodynamically spontaneous nature. The selective removal of defect channels under Lewis acidic conditions, induced by metal ion alcoholysis/hydrolysis, facilitates the introduction of metal atoms into ZIF cavities. The resulting single-atom catalyst, after pyrolysis, features a three-dimensional (3D) multichannel structure, high surface area, and uniformly dispersed metal atoms within the N-doped carbon matrix, establishing it as an exceptional catalyst for the oxygen reduction reaction (ORR). Our findings highlight the potential of using metal etching in defect-engineered metal-organic frameworks (MOFs) for single-atom catalyst preparation, paving the way for the next generation of high-performance, cost-effective ORR catalysts in sustainable energy systems.

Electrochemical converting CO2 to CO via single atom catalyst is an effective strategy for reducing CO2 concentration in the atmosphere and achieving a carbon‐neutral cycle. However, the relatively low CO2 concentration in industrial processes and large energy barriers for activating CO2 severely obstruct the actual application. Reasonably modulating the coordination shell of the active center is an effective strategy to enhance the activity of single atom catalysts. Herein, a well‐designed single‐atom electrocatalyst Ni‐N3S1 is developed via a large‐scale synthesis strategy. The constructed Ni‐N3S‐C exhibits a superior catalytic activity than Ni‐N4‐C for CO2 to CO conversion in H‐type cells, and the industrial‐level current density with excellent durability at a wide pH range can be achieved in gas‐diffusion flow cells. Experimental results and density functional theory (DFT) calculation demonstrate that introducing low electronegative S in an active center can significantly regulate the electronic structure of the active site, promoting the CO2 adsorption capacity and decreasing the energy barrier of *COOH formation, thus the larger size and flexibility of sulfur mitigate the nickel agglomeration and enhance the stability of Ni‐N3S‐C catalyst. This work provides an effective strategy for designing highly active single‐atom catalysts for electrocatalysis via modulating the coordination shell of reactive sites.

Visible‐light‐driven photocatalytic oxidation by photogenerated holes has immense potential for environmental remediation applications. While the electron‐mediated photoreduction reactions are often at the spotlight, active holes possess a remarkable oxidation capacity that can degrade recalcitrant organic pollutants, resulting in nontoxic byproducts. However, the random charge transfer and rapid recombination of electron–hole pairs hinder the accumulation of long‐lived holes at the reaction center. Herein, a novel method employing defect‐engineered indium (In) single‐atom photocatalysts with nitrogen vacancy (Nv) defects, dispersed in carbon nitride foam (In‐Nv‐CNF), is reported to overcome these challenges and make further advances in photocatalysis. This Nv defect‐engineered strategy produces a remarkable extension in the lifetime and an increase in the concentration of photogenerated holes in In‐Nv‐CNF. Consequently, the optimized In‐Nv‐CNF demonstrates a remarkable 50‐fold increase in photo‐oxidative degradation rate compared to pristine CN, effectively breaking down two widely used antibiotics (tetracycline and ciprofloxacin) under visible light. The contaminated water treated by In‐Nv‐CNF is completely nontoxic based on the growth of Escherichia coli. Structural–performance correlations between defect engineering and long‐lived hole accumulation in In‐Nv‐CNF are established and validated through experimental and theoretical agreement. This work has the potential to elevate the efficiency of overall photocatalytic reactions from a hole‐centric standpoint.

No abstract available

Nitrite (NO2−) is responsible for several physiological processes but can be harmful in excess. With rising exposure from food preservatives, fertilizers, and pollutants, accurate nitrite assessment is crucial for health and environmental safety. Different methods have been employed for its determination, with electrochemical sensors showcasing great promise. Single atom catalysts (SACs) are a class of nanomaterials that consists of isolated catalytic metal atoms anchored on conductive supports, which exhibit unique electronic properties with great promise for this application. The performance of these materials can be enhanced even more by incorporating a secondary metal in the catalyst structure. This leads to the creation of more surface‐active sites and enables the facilitation of multi‐step reactions. Herein, a bimetallic single atom catalyst (FeCoSAN) is synthesized through a single step laser assisted solid‐process by anchoring iron and cobalt atoms while simultaneously creating a laser‐scribed graphene (LSG) support. The presence of Fe and Co atoms is verified by high‐angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM) and X‐ray absorption spectroscopy (XANES and EXAFS). Through electrochemical testing, the bimetallic system demonstrated excellent capabilities for determination of NO2, achieving up to 100% more efficiency, in comparison with bare LSG, with a detection limit of 2.42 µm and a sensitivity value of 515.07 µA mm−1 cm−2 over a linear range from 5.0 to 1666 µm. This highlights their potential for in vivo and point‐of‐care sensing applications.

Gold single-atom catalysts (SACs) exhibit outstanding reactivity in acetylene hydrochlorination to vinyl chloride, but their practical applicability is compromised by current synthesis protocols, using aqua regia as chlorine-based dispersing agent, and their high susceptibility to sintering on non-functionalized carbon supports at >500 K and/or under reaction conditions. Herein, a sustainable synthesis route to carbon-supported gold nanostructures in bimetallic catalysts is developed by employing salts as alternative chlorine source, allowing for tailored gold dispersion, ultimately reaching atomic level when using H2 PtCl6 . To rationalize these observations, several synthesis parameters (i.e., pH, Cl-content) as well as the choice of metal chlorides are evaluated, hinting at the key role of platinum in promoting a chlorine-mediated dispersion mechanism. This can be further extrapolated to redisperse large gold agglomerates (>70 nm) on carbon carriers into isolated atoms, which has important implications for catalyst regeneration. Another key role of platinum single atoms is to inhibit the sintering of their spatially isolated gold-based analogs up to 800 K and during acetylene hydrochlorination, without compromising the intrinsic activity of Au(I)-Cl active sites. Accordingly, exploiting cooperativity effects of a second metal is a promising strategy towards practical applicability of gold SACs, opening up exciting opportunities for multifunctional single-atom catalysis.

The development of a quantitative electrochemical method for H2O2 detection is crucial as it enables the real-time assessment of both bleaching agent residues in food and oxidative stress in cancer cells. The single-atom Co catalyst Co SAs@ZIF-NC was prepared using a bimetallic ZIF-8-67 precursor via a template-confined synthesis strategy. Successful synthesis was confirmed through comprehensive characterization of its structure and morphology using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller method, and X-ray absorption near edge structure. The as-synthesized Co SAs@ZIF-NC was immobilized on the surface of a pencil-lead graphite electrode, enabling the electrochemical detection of H2O2. The H2O2 sensor showed excellent analytical performance for H2O2 detection, with a linear range of 1-12000 μM, a detection limit of 0.21 μM, and a sensitivity of 2395.54 μA·mM-1·cm-2 (S/N = 3), alongside reliable selectivity, stability, and reproducibility. It was successfully applied to determine H2O2 residues in food and monitor extracellular H2O2 levels in A549 cells. Therefore, this paper proposes a novel material design strategy for single-atom catalysts for electrochemical H2O2 sensing.

Developing an efficient single-atom material (SAM) synthesis and exploring the energy-related catalytic reaction are important but still challenging. A polymerization-pyrolysis-evaporation (PPE) strategy was developed to synthesize N-doped porous carbon (NPC) with anchored atomically dispersed Fe-N4 catalytic sites. This material was derived from predesigned bimetallic Zn/Fe polyphthalocyanine. Experiments and calculations demonstrate the formed Fe-N4 site exhibits superior trifunctional electrocatalytic performance for oxygen reduction, oxygen evolution, and hydrogen evolution reactions. In overall water splitting and rechargeable Zn-air battery devices containing the Fe-N4 SAs/NPC catalyst, it exhibits high efficiency and extraordinary stability. This current PPE method is a general strategy for preparing M SAs/NPC (M=Co, Ni, Mn), bringing new perspectives for designing various SAMs for catalytic application.

Dual‐atom catalysts (DACs) have emerged as a novel area of investigation in lithium–oxygen (Li‐O2) batteries due to their distinctive synergistic mechanisms. However, achieving precise control of the active site structure and unraveling the synergistic effects of bimetallic species remains a significant challenge. Here, the study reports a pre‐encapsulated pyrolysis strategy using a Co‐based Robson‐type binuclear complex as a precursor to mediate the synthesis of dual single‐atom Co (Co‐DAC) with precise angstrom‐scale inter‐site distance configuration, serving as an efficient catalyst for Li‐O2 batteries. The tailored structure induces significant charge redistribution, reducing crystal field splitting energy (ΔO). The high‐spin Co species generate a strong electronic driving force, forming flexible σ and δ‐like bonds with the crucial oxygen intermediate (*O). Simultaneously, enhanced Co‐O spin‐orbit coupling facilitates electron transport along the bridging O‐channel, forming highly active Co‐O‐O‐Co electron chains that synergistically adsorb *O, establishing a favorable reaction pathway. Significant optimization of Li‐O2 batteries redox kinetics is achieved based on the well‐defined local structure of dual single‐atom Co sites. This work enhances the understanding of the dependence between rational design of custom structures and corresponding electron transfer dynamics, while providing new strategies and theoretical guidance for DACs to help develop high‐performance Li‐O2 batteries.

A general synthesis and the coordination environment control of single-atom catalysts (SACs) remain great challenges. Herein, a general host-guest cooperative protection strategy has been developed to construct SACs by introducing polypyrrole (PPy) into a bimetallic metal-organic framework. As a representative, the introduction of Mg 2+ in MgNi-MOF-74 extends the spatial distance of adjacent Ni atoms; the PPy guests serve as N source to stabilize the isolated Ni atoms during pyrolysis. As a result, a series of single-atom Ni catalysts (named Ni SA -N x -C) with different N coordination numbers have been fabricated by regulating the pyrolysis temperature. Significantly, the Ni SA -N 2 -C catalyst, with the lowest N coordination number, achieves very high CO Faradaic efficiency (98%) and turnover frequency (1622 h -1 ), far superior to those of Ni SA -N 3 -C and Ni SA -N 4 -C, in electrocatalytic CO 2 reduction. Theoretical calculations reveal that the low N coordination number of single-atom Ni sites in Ni SA -N 2 -C is favorable to the formation of COOH* intermediate and thus accounts for its superior activity.

Given a desired property, locating relevant materials is always highly desired but very challenging in a range of areas, including heterogeneous catalysis. Obviously, object-oriented design/screening is an ideal solution to this problem. Herein, we develop an inverse catalyst design workflow in Python (CATIDPy) that utilizes a genetic-algorithm-based global optimization method to guide on-the-fly density functional theory calculations, successfully realizing the highly accelerated location of active single-atom alloy (SAA) catalysts for the hydrogen evolution reaction (HER). 70 binary and 752 ternary SAA candidate catalysts are identified for the HER. Furthermore, via considering the segregation stability and cost of materials, we extracted 6 binary and 142 ternary SAA candidate catalysts that are recommended for experimental synthesis. Remarkably, guided by these theoretical identifications, homogeneously dispersed Ni-based bimetallic catalysts (e.g., NiMo, NiAl, Ni3Al, NiGa, and NiIn) were synthesized experimentally to test the reliability of the CATIDPy workflow, and they showed superior HER performance to bare Ni foam, indicating huge potential for use in real-world water electrolysis techniques. Perhaps more importantly, these results demonstrate the capacity of such a proposed approach for investigating unexplored chemical spaces to efficiently design promising catalysts without knowledge from the expert domain, which has far-reaching implications.

Single-atom transition metal-based nitrogen-doped carbon (M-Nx-C) is regarded as high-efficiency and cost-effectiveness alternatives to replace noble metal catalysts for oxygen reduction reaction (ORR) in renewable energy storage and conversion devices. In this work, rich FeCo dual-single atoms were efficiently entrapped into N-doped carbon nanocages (FeCo DSAs-NCCs) by simple pyrolysis of the bimetallic precursors doped zeolitic imidazolate framework-8 (ZIF-8), as affirmed by a series of characterizations. The graphitization degree of the N-doping carbon substrate was regulated by modulating the pyrolysis temperature and the types of the metal salts. The typical catalyst substantially improved the alkaline ORR performance, with the onset potential (Eonset) of 0.99 V (vs. RHE) and half-wave potential (E1/2) of 0.88 V (vs. RHE). Ultimately, the catalyst-assembled Zn-air battery possessed a higher open-circuit voltage of 1.501 V, larger power density of 123.7 mW cm-2, and outstanding durability for 150 h. This study provides a guide on developing ORR catalysts for electrochemical energy conversion and storage technology.

A well-defined catalyst with dual Ni/Fe atomic active sites was created using a pyrolysis-free approach. The as-made catalyst was used for overall electrochemical water splitting in both acidic and alkaline electrolytes with low overpotentials. Catalysts capable of electrochemical overall water splitting in acidic, neutral, and alkaline solution are important materials. This work develops bifunctional catalysts with single atom active sites through a pyrolysis-free route. Starting with a conjugated framework containing Fe sites, the addition of Ni atoms is used to weaken the adsorption of electrochemically generated intermediates, thus leading to more optimized energy level sand enhanced catalytic performance. The pyrolysis-free synthesis also ensured the formation of well-defined active sites within the framework structure, providing ideal platforms to understand the catalytic processes. The as-prepared catalyst exhibits efficient catalytic capability for electrochemical water splitting in both acidic and alkaline electrolytes. At a current density of 10 mA cm^−2, the overpotential for hydrogen evolution and oxygen evolution is 23/201 mV and 42/194 mV in 0.5 M H_2SO_4 and 1 M KOH, respectively. Our work not only develops a route towards efficient catalysts applicable across a wide range of pH values, it also provides a successful showcase of a model catalyst for in-depth mechanistic insight into electrochemical water splitting.

The traditional biocatalytic precipitation (BCP) strategy often required the participation of H2O2, but H2O2 had the problem of self-decomposition, which prevented its application in quantitative analysis. This work first found that a bimetallic single-atom catalyst (Co/Zn-N-C SAC) could effectively activate dissolved O2 to produce reactive oxygen species (ROS) due to its superior oxidase (OXD)-like activity. Experimental investigations demonstrated that Co/Zn-N-C SAC preferred to produce highly active hydroxyl radicals (•OH), which oxidized 3-amino-9-ethyl carbazole (AEC) to produce reddish-brown insoluble precipitates. Based on this property, a unique oxygen-activated photoelectrochemical (PEC) biosensor was developed for chloramphenicol (CAP) detection. Cesium platinum bromide nanocrystals (Cs2PtBr6 NCs) were a new type of halide perovskite with lead-free, narrow band gaps, and water-oxygen resistance. Cs2PtBr6 NCs showed excellent cathodal PEC performance without an exogenous coreactant and were first used for PEC detection. As a "proof-of-concept application", Co/Zn-N-C SAC was introduced onto the surface of Cs2PtBr6 NCs by using the CAP dual-aptamer sandwich strategy. Co/Zn-N-C SAC activated dissolved O2 to produce ROS, which oxidized AEC to produce precipitates, quenching the cathodal PEC signal of Cs2PtBr6 NCs for CAP detection. In summary, this work first used SAC to overcome the restriction of the traditional enzymatic BCP strategy requiring H2O2, improved the stability and accuracy of quantitative analysis, and also broadened the application range of coreactant-free perovskite-type PEC biosensors.

No abstract available

Iron and nitrogen co-doped carbon materials (Fe-N-C) have garnered widespread attention owing to their highly active Fe-N4 sites. Here, we proposed a novel approach for synthesizing bimetallic single-atom catalysts by introducing Cu atoms into Fe-N-C. The resultant Fe-Cu-NC catalyst exhibited a large specific surface area. Moreover, it had a superior half-wave potential of 0.890 V (vs. RHE) in alkaline media. Density functional theory calculations disclosed that the introduction of Cu augmented the adsorption capacity of Fe-N4 active sites concerning oxygen intermediates, thus accelerating the reaction pathway and markedly enhancing the catalytic activity of the oxygen reduction reaction (ORR). When employed as the cathode of a zinc-air battery, the Fe-Cu-NC catalyst manifested superior performance, with a top power density reaching 183.1 mW cm-2 and a specific capacity reaching 787 mAh g-1Zn. This study put forward a promising methodology to refine and boost the ORR activities of Fe-N-C-based catalysts with atomic dispersion.

No abstract available

Chlorinated organic pollutants are highly toxic and widespread in the environment, which cause ecological risk and threaten the human health. Chlorinated pollutants are difficult to degrade and mineralize by the conventional advanced oxidation process as the C-Cl bond is resistant to reactive oxygen species oxidation. Herein, we designed a bifunctional Fe/Cu bimetallic single-atom catalyst anchored on N-doped porous carbon (FeCuSA-NPC) for the electro-Fenton process, in which chlorinated pollutants are dechlorinated on single-atom Cu and subsequently oxidized by the ·OH radical produced from O2 conversion on single-atom Fe. Benefitting from the synergistic effect between dechlorination on single-atom Cu and ·OH oxidation on single-atom Fe, the chlorinated organic pollutants can be efficiently degraded and mineralized. The mass activity for chlorinated organic pollutant degradation by FeCuSA-NPC is 545.1-1374 min-1 gmetal-1, excessing the highest value of the reported electrocatalyst. Moreover, FeCuSA-NPC is demonstrated to be pH-universal, long-term stable, and environment friendly. This work provides a new insight into the rational design of a bifunctional electrocatalyst for efficient removal of chlorinated organic pollutants.

No abstract available

One‐pot synthesis of acetamides, benzimidazoles, and benzothiazoles are central reactions for synthesizing pharmaceuticals and fine chemicals. Despite tremendous progress in heterogeneous catalysis, the synthesis of these nitrogen‐containing compounds still remains challenging. Here, we report an efficient, simple, and cost‐effective nitrogen‐doped CeO2‐supported Co single‐atom catalyst (SAC) (Co/N‐CeO2) enabled synthesis of acetamides, benzimidazoles, and benzothiazoles. As far as we know, this is the first to report that SACs catalyze the synthesis of acetamides, benzimidazoles, and benzothiazoles. Detailed spectroscopic characterization revealed the structure of catalytic center. Harnessing the catalytic activity of SACs, the work offers promising routes for future synthesis of heterocycles.

Rapid and accurate detection of human epidermal growth factor receptor 2 (HER2) is crucial for the early diagnosis and prognosis of breast cancer. In this study, we reported an iron–manganese ion N-doped carbon single-atom catalyst (FeMn-NCetch/SAC) bimetallic peroxidase mimetic enzyme with abundant active sites etched by H2O2 and further demonstrated unique advantages of single-atom bimetallic nanozymes in generating hydroxyl radicals by density functional theory (DFT) calculations. As a proof of concept, a portable device-dependent electrochemical-photothermal bifunctional immunoassay detection platform was designed to achieve reliable detection of HER2. In the enzyme-linked reaction, H2O2 was generated by substrate catalysis via secondary antibody-labeled glucose oxidase (GOx), while FeMn-NCetch/SAC nanozymes catalyzed the decomposition of H2O2 to form OH*, which catalyzed the conversion of 3,3′,5,5′-tetramethylbenzidine (TMB) to ox-TMB. The ox-TMB generation was converted from the colorimetric signals to electrical and photothermal signals by applied potential and laser irradiation, which could be employed for the quantitative detection of HER2. With the help of this bifunctional detection technology, HER2 was accurately detected in two ways: photothermally, with a linear scope of 0.01 to 2.0 ng mL–1 and a limit of detection (LOD) of 7.5 pg mL–1, and electrochemically, with a linear scope of 0.01 to 10 ng mL–1 at an LOD of 3.9 pg mL–1. By successfully avoiding environmental impacts, the bifunctional-based immunosensing strategy offers strong support for accurate clinical detection.

Abstract Carbon‐heteroatom cross‐coupling reactions have become indispensable tools in synthetic chemistry. However, the formation of carbon–sulfur (C─S) bonds, which are essential for producing thioethers used in pharmaceuticals, agrochemicals, and advanced materials, remains significantly underdeveloped. Industrial C─S coupling methods still rely on expensive, homogeneous catalysts that suffer from poor recyclability and are susceptible to sulfur‐induced deactivation. In this work, we report a copper single‐atom catalyst, where Cu sites are atomically dispersed on mesoporous graphitic carbon nitride, to enable efficient, selective, and recyclable C─S cross‐coupling reactions under mild conditions and on a gram scale. The catalyst exhibits excellent resistance to thiol poisoning and maintains high performance over multiple catalytic cycles. Advanced characterization techniques, including aberration‐corrected electron microscopy, X‐ray absorption spectroscopy, and single‐atom‐sensitive electron energy loss spectroscopy, confirm the atomic dispersion and stable coordination environment of Cu sites. Combined with density functional theory simulations and radical scavenging experiments, our mechanistic investigations support a concerted oxidative addition pathway, which excludes radical intermediates. These results provide key insights into heterogeneous C─S coupling and demonstrate the power of single‐atom catalysts in addressing long‐standing challenges in sulfur chemistry, paving the way toward greener and more scalable processes for fine chemical and pharmaceutical synthesis.

Electrocatalytic reduction of nitrate (NO3-, NO3RR) on single-atom copper catalysts (Cu-SACs) offers a sustainable approach to ammonia (NH3) synthesis using NO3- pollutants as feedstocks. Nevertheless, this process suffers from inferior NO3RR kinetics and nitrite accumulation owing to the linear scaling relation limitations for SACs. To break these limitations, a single-atom Cu-bearing tungsten oxide catalyst (Cu1/WO3) was developed, which mediated a unique dual-driven NO3RR process. Specifically, WO3 dissociated water molecules and supplied the Cu1 site with ample protons, while the Cu1 site in an electron-deficient state converted NO3- to NH3 efficiently. The Cu1/WO3 delivered an impressive NH3 production rate of 1274.4 mgN h-1 gCu-1, a NH3 selectivity of 99.2%, and a Faradaic efficiency of 93.7% at -0.60 V, surpassing most reported catalysts. Furthermore, an integrated continuous-flow system consisting of NO3RR cell and vacuum-driven membrane separator was developed for NH3 synthesis from nitrate-contaminated water. Fed with the Yangtze River water containing ~22.5 mg L-1 of NO3--N, this system realized an NH3 production rate of 325.9 mgN h-1 gCu-1 and a collection efficiency of 98.3% at energy consumption of 17.11 kwh gN-1. This study provides a new dual-driven concept for catalyst design and establishes a foundation for sustainable NH3 synthesis from waste.

Single‐atom catalysts (SACs), where individual metal atoms are anchored on support, hold great promise for electrocatalytic hydrogen evolution reactions (HERs). The inherent simplicity of the single‐atom center restricts opportunities for further enhancement. Binuclear SACs, incorporating two different metal sites, can further improve HER kinetics. However, the underlying mechanisms of the HER at the binuclear sites are complex and not fully understood, hampering the design of new efficient catalyst structures. Here, a comprehensive investigation is presented into phosphorus‐doped iron and cobalt bimetallic SACs supported on nitrogen‐doped graphitic carbon (P/FeCo‐NC), focusing on the potential mechanisms underpinning their enhanced HER activity. P/FeCo‐NC exhibits overpotentials of 38 and 95 mV at 10 mA cm2 in 0.5 m H2SO4 and 1 m KOH, respectively, nearing the acidic performance of commercial Pt/C (33 mV). Theoretical studies reveal that the phosphorus bridge significantly alters the electronic properties of the Fe active sites, while the adjacent Co atoms modulate the electronic environment, further optimizing the hydrogen adsorption‐free energy toward more favorable kinetics. This work highlights the structure‐activity relationships of bimetallic SACs and opens perspectives for future applications.

No abstract available

Atom-dispersed low-coordinated transition metal-Nx catalysts exhibit excellent efficiency in activating peroxydisulfate (PDS) for environmental remediation. However, their catalytic performance is limited due to metal-N coordination number and single-atom loading amount. In this study, low-coordinated nitrogen-doped graphene oxide (GO) confined single-atom Mn catalyst (Mn-SA/NGO) was synthesized by molten salt-assisted pyrolysis and coupled to PDS for degradation of tetracycline (TC) in water. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM) and X-ray absorption fine structure spectroscopy (XAFS) analysis showed the successful doping of single-atom Mn (weight percentage 1.6%) onto GO and the formation of low-coordinated Mn-N2 sites. The optimized parameters obtained by Box-Behnken Design achieved 100% TC removal in both prediction and experimental results. The Mn-SA/NGO+PDS system had strong anti-interference ability for TC removal in the presence of anions. Besides, Mn-SA/NGO possessed good reusability and stability. O2•-, •OH, and 1O2 were the main active species for TC degradation, and the TC mineralization reached 85.1%. Density functional theory (DFT) calculations confirmed that the introduction of single atoms Mn could effectively enhance adsorption and activation of PDS. The findings provide a reference for the synthesis of high-performance single-atom catalysts for effective removal of antibiotics.

Metal sites at the edge of the carbon matrix possess unique geometric and electronic structures, exhibiting higher intrinsic activity than in‐plane sites. However, creating single‐atom catalysts with high‐density edge sites remains challenging. Herein, the hierarchically ordered pore engineering of metal–organic framework‐based materials to construct high‐density edge‐type single‐atomic Ni sites for electrochemical CO2 reduction reaction (CO2RR) is reported. The created ordered macroporous structure can expose enriched edges, further increased by hollowing the pore walls, which overcomes the low edge percentage in the traditional microporous substrates. The prepared single‐atomic Ni sites on the ordered macroporous carbon with ultra‐thin hollow walls (Ni/H‐OMC) exhibit Faraday efficiencies of CO above 90% in an ultra‐wide potential window of 600 mV and a turnover frequency of 3.4 × 104 h−1, much superior than that of the microporous material with dominant plane‐type sites. Theory calculations reveal that NiN4 sites at the edges have a significantly disrupted charge distribution, forming electron‐rich Ni centers with enhanced adsorption ability with *COOH, thereby boosting CO2RR efficiency. Furthermore, a Zn–CO2 battery using the Ni/H‐OMC cathode shows an unprecedentedly high power density of 15.9 mW cm−2 and maintains an exceptionally stable charge–discharge performance over 100 h.

Single-atom catalysts (SACs) are highly dependent on the properties of their supports, and organic polymers have recently emerged as promising candidates due to their tunable physicochemical properties and diverse functional groups. However, the high-temperature carbonization commonly required for conventional organic polymer-supported SAC fabrication often leads to the loss of these functional groups, thus weakening metal-support interactions and catalytic performance accordingly. Herein, we report a sustainable strategy to synthesize nitrogen-functionalized lignin-based phenolic resin (N-LPR) supports for stabilizing atomically dispersed Pd without carbonization. Using NH3·H2O as both the nitrogen source and catalyst, high molecular weight lignin fractions (L3) were transformed into N-L3PR-50% supports with a unique nano-chain-like structure, high surface area, and abundant amine groups, which can directly anchor Pd sites under room temperature. The resulting Pd@N-L3PR-50% catalyst achieved approximately 100% vanillin conversion and 97.91% selectivity for 2-methoxy-4-methylphenol at 80°C with excellent cycle stability and adaptability to lignin-derived aldehydes, benefiting from the stable Pd-N coordination and the good adsorption capacity provided by the N-L3PR-50% support. Consequently, this work not only demonstrates a straightforward non-carbonation strategy to prepare lignin-based SACs for potent biomass-derived chemical transformations but also provides a novel avenue for the application of conventional multifunctional organic polymers as support for SACs.

Understanding and controlling the structure-activity relationship of single atom catalysts (SACs) is crucial for optimizing their catalytic performance. This study investigated the influence of montmorillonite (MT) as a support material on the microstructure of SACs, and how these influences modulate the catalytic performance and mechanism of peroxymonosulfate (PMS) activation. The enrichment effect within the MT interlayer space significantly enhanced the interaction between organic pollutant molecules, PMS, and active sites, thereby improving adsorption capacity and mass transfer efficiency. This enhancement increased the likelihood of subsequent peroxide bond cleavage, enabling the system to exhibit a greater capacity to generate high-valent Co (IV)-oxo and free radicals (SO4•- and •OH), leading to a higher removal efficiency of sulfamethoxazole (SMX). The introduction of MT altered the pathway of SMX removal, and the CoSAC@MT/PMS system predominantly degraded SMX into intermediate products with lower molecular weights and negligible fluorescence signals. Additionally, the incorporation of MT significantly boosted the yield of SACs synthesized via traditional pyrolysis methods, offering a novel strategy to reduce preparation costs and achieve large-scale synthesis.

Single‐atom (SA) catalysts exhibit high activity in various reactions because there are no inactive internal atoms. Accordingly, SA cocatalysts are also an active research fields regarding photocatalytic hydrogen (H2) evolution which can be generated by abundant water and sunlight. Herein, it is investigated whether 10 transition metal elements can work as an SA on graphitic carbon nitride (g‐C3N4; i.e., gCN), a promising visible‐light‐driven photocatalyst. A method is established to prepare SA‐loaded gCN at high loadings (weight of ≈3 wt.% for Cu, Ni, Pd, Pt, Rh, and Ru) by modulating the photoreduction power. Regarding Au and Ag, SAs are formed with difficulty without aggregation because of the low binding energy between gCN and the SA. An evaluation of the photocatalytic H2‐evolution activity of the prepared metal SA‐loaded gCN reveals that Pd, Pt, and Rh SA‐loaded gCN exhibits relatively high H2‐evolution efficiency per SA. Transient absorption spectroscopy and electrochemical measurements reveal the following: i) Pd SA‐loaded gCN exhibits a particularly suitable electronic structure for proton adsorption and ii) therefore they exhibit the highest H2‐evolution efficiency per SA than other metal SA‐loaded gCN. Finally, the 8.6 times higher H2‐evolution rate per active site of Pd SA is achieved than that of Pd‐nanoparticles cocatalyst.

A single-atom Ce-modified α-Fe2O3 catalyst (Fe0.93Ce0.07Ox catalyst with 7% atomic percentage of Ce) was synthesized by a citric acid-assisted sol-gel method, which exhibited excellent performance for selective catalytic reduction of NOx with NH3 (NH3-SCR) over a wide operating temperature window. Remarkably, it maintained ∼93% NO conversion efficiency for 168 h in the presence of 200 ppm SO2 and 5 vol % H2O at 250 °C. The structural characterizations suggested that the introduction of Ce leads to the generation of local Fe-O-Ce sites in the FeOx matrix. Furthermore, it is critical to maintain the atomic dispersion of the Ce species to maximize the amounts of Fe-O-Ce sites in the Ce-doped FeOx catalyst. The formation of CeO2 nanoparticles due to a high doping amount of Ce species leads to a decline in catalytic performance, indicating a size-dependent catalytic behavior. Density functional theory (DFT) calculation results indicate that the formation of oxygen vacancies in the Fe-O-Ce sites is more favorable than that in the Fe-O-Fe sites in the Ce-free α-Fe2O3 catalyst. The Fe-O-Ce sites can promote the oxidation of NO to NO2 on the Fe0.93Ce0.07Ox catalyst and further facilitate the reduction of NOx by NH3. In addition, the decomposition of NH4HSO4 can occur at lower temperatures on the Fe0.93Ce0.07Ox catalyst containing atomically dispersed Ce species than on the α-Fe2O3 reference catalyst, resulting in the good SO2/H2O resistance ability in the NH3-SCR reaction.

The performance of oxygen evolution reaction (OER) catalysts heavily depends on intrinsically active and robust sites as well as high active site number, which poses challenges in catalyst design concerning composition and structure. This study presents a general oxygen-vacancy anchoring strategy for preparing oxide-based 4d/5d transition metal single-atom 2D materials as efficient and robust OER catalysts. In a typical synthesis, Keggin-structure polyoxometalate [PW12O40]3- clusters decompose into tetrahedral WO42- anions, which in situ adhere to the newly nucleated metal (Co, Fe, Ni) hydroxide (M(OH)x) due to the latter's abundant oxygen vacancies, ensuring a uniform distribution of W single atoms. The anchoring of W stabilizes the ultrathin structure, resulting in the annealed W-Co3O4 exhibiting a specific surface area 5-7 times greater than that of pure Co3O4, even though W has three times the atomic weight of Co. Moreover, the strengthened adsorption of OH induced by W breaks the surface structural integrity of Co3O4 to form a highly active oxyhydroxide, while the increased distortion in Co-O octahedrons further enhances the intrinsic activity. As a result, the catalyst shows a low η10 of 261 mV in alkaline media, 84 mV lower than that of pure Co3O4, and an excellent stability of over 290 h. This places it among the best OER catalysts, particularly in comparison to low-activity Ni or -unstable NiFe alternatives.

Selective hydrogenation of 1,3-butadiene to butenes is an effective way to eliminate the minor 1,3-butadiene impurities, which can cause intractable issues of catalyst deactivation in the C4 olefins upgrading processes. To this end, Pd single-atom catalysts (SACs) exhibit remarkable selectivity to desired butene products due to the adsorption configuration of 1,3-butadiene in a mono-π mode. However, it is still a grand challenge to prepare thermally stable Pd SACs with conventional synthetic methods. Herein, we acquired Pd SACs via the selective encapsulation strategy exploiting classical strong metal-support interaction, during which Pd nanoparticles are more prone to be encapsulated by the oxide overlayer than Pd single atoms, thus Pd single atoms exclusively stay exposed to the catalytic environment. Various characterizations, such as aberration-corrected high-angle annular dark-field scanning transmission electron microscopy, electron energy loss spectroscopy, together with CO adsorbed in-situ diffuse reflectance infrared Fourier transform spectra, have collectively demonstrated the successful synthesis of Pd SACs on CeO2 support when we adjusted the reductive temperature to 600 °C (Pd/CeO2-H600). The as-obtained Pd/CeO2-H600 gives excellent catalytic performances in the selective hydrogenation of 1,3-butadiene with conversion of almost 100% and butenes selectivity of above 98% at 100 °C. Moreover, the conversion of 99% and butenes selectivity of 97.5% can also remain nearly unchanged for 60 h at a weight hourly space velocity of 60,000 mL/gcat/h. This work illustrates the effectiveness of this selective encapsulation strategy to construct Pd SACs and can probably provide a prospective avenue to prepare various SACs for selective hydrogenation processes.

Pt atoms stabilized by alkaline ions efficiently and selectively catalyze CO oxidation under H2 rich conditions (PROX). The preferential oxidation of CO (PROX) in hydrogen-rich fuel gas streams is an attractive option to remove CO while effectively conserving energy and H2. However, high CO conversion with concomitant high selectivity to CO2 but not H2O is challenging. Here, we report the synthesis of high-loading single Pt atom (2.0 weight %) catalysts with oxygen-bonded alkaline ions that stabilize the cationic Pt. The synthesis is performed in aqueous solution and achieves high Pt atom loadings in a single-step incipient wetness impregnation of alumina or silica. Promisingly, these catalysts have high CO PROX selectivity even at high CO conversion (~99.8% conversion, 70% selectivity at 110°C) and good stability under reaction conditions. These findings pave the way for the design of highly efficient single-atom catalysts, elucidate the role of ─OH species in CO oxidation, and confirm the absence of a support effect for our case.

No abstract available

Platinum single atoms are loaded into mesoporous carbon spheres to give high electrocatalytic performance for hydrogen generation. Constructing atomically dispersed platinum (Pt) electrocatalysts is essential to build high-performance and cost-effective electrochemical water-splitting systems. We present a novel strategy to realize the traction and stabilization of isolated Pt atoms in the nitrogen-containing porous carbon matrix (Pt@PCM). In comparison with the commercial Pt/C catalyst (20 weight %), the as-prepared Pt@PCM catalyst exhibits significantly boosted mass activity (up to 25 times) for hydrogen evolution reaction. Results of extended x-ray absorption fine structure investigation and density functional theory calculation suggest that the active sites are associated with the lattice-confined Pt centers and the activated carbon (C)/nitrogen (N) atoms at the adjacency of the isolated Pt centers. This strategy may provide insights into constructing highly efficient single-atom catalysts for different energy-related applications.

Xylene, a volatile organic compound that is widely used in industrial processes, can pose significant health risks when present in ambient air. Accurate detection of xylene at low concentrations is crucial for environmental monitoring and industrial safety but remains challenging. This study employed a novel Pt atomic cluster (0.01%-1.5% weight percentage)-decorated Fe2(MoO4)3 hollow microsphere sensor (Pt-FMO) using the atomic layer deposition method. Chemical and structural analyses confirmed the presence of isolated Pt atoms and clusters. Sensing performance studies revealed that 0.2% Pt-FMO exhibited a 47-fold increase in the gas response to xylene at 100 °C; moreover, it demonstrated rapid response and recovery time, an ultralow detection limit at sub-parts-per-million levels, good selectivity, and long-term stability. The high surface-to-volume ratio of the Pt atomic clusters significantly modified the surface chemical environment by increasing the adsorbed oxygen species while preserving surface morphology. Additionally, the Pt cluster catalyzed xylene oxidation, and the non-aggregated FMO hollow microspheres chemisorbed more oxygen molecules during the sensing process. The synergistic effect of Pt atomic clusters and FMO hollow microspheres makes this sensor a promising candidate for applications in environmental and industrial gas monitoring.

In recent years, single-atom catalysts attracted lots of attention because of their high catalytic activity, selectivity, stability, maximum atom utilization, exceptional performance, and low cost. Single-atom catalyst contains isolated individual atom which are coordinated with the surface atoms of support such as a metal oxide or 2d - materials. In this review article, we present the advancement in single-atom catalysis in recent years with a focus on the various synthesis methods and their application in catalytic reactions. We also demonstrate the reaction mechanism of a single-atom catalyst for different catalytic reactions from theoretical aspects using density functional theory.

Single-atom catalysts represent an essential and ever-growing family of heterogeneous catalysts. Recent studies indicate that besides the valuable catalytic properties provided by single-atom active sites, the presence of single-atom sites on the catalyst substrates may significantly influence the population of supported metal nanoparticles coexisting with metal single atoms. Treatment of ceria-based single-atom catalysts in oxidizing or reducing atmospheres was proven to provide precise experimental control of the size of the supported Pt nanoparticles, and, correspondingly, control of catalyst activity and stability. Based on dedicated surface science experiments, ab-initio calculations and kinetic Monte-Carlo simulations we demonstrate that the morphology of Pt nanoparticle population on ceria surface is a result of a competition for Pt atoms between Pt single-atom sites and Pt nanoparticles. In oxidizing atmosphere, Pt single-atom sites provide strong bonding to single Pt atoms and Pt nanoparticles shrink. In reducing atmosphere, Pt single atom sites are depopulated and Pt nanoparticles grow. We formulate a generic model of Pt redispersion and coarsening on ceria substrates. Our model provides a unified atomic-level explanation for a variety of metal nanoparticle dynamic processes observed in single-atom catalysts under stationary or alternating oxidizing/reducing atmospheres, and allows to classify the conditions when nanoparticle ensembles on single-atom catalysts substrates can be stabilized against Ostwald ripening.

Endohedral fullerenes are perfect nanolaboratories for the study of magnetism. The substitution of a diamagnetic scandium atom in Dy2ScN@C80 with gadolinium decreases the stability of a given magnetization and demonstrates Gd to act as a single atom catalyst that accelerates the reaching of thermal equilibrium. X-ray magnetic circular dichroism at the M4,5 edges of Gd and Dy shows that the Gd magnetic moment follows the sum of the external and the dipolar magnetic field of the two Dy ions and compared to Dy2ScN@C80 a lower exchange barrier is found between the ferromagnetic and the antiferromagnetic Dy configuration. The Arrhenius equilibration barrier as obtained from superconducting quantum interference device magnetometry is more than one order of magnitude larger, though a much smaller prefactor imposes faster equilibration in Dy2GdN@C80. This sheds light on the importance of the angular momentum balance in magnetic relaxation.

Catalysis has entered everyday life through a number of technological processes relying on different catalytic systems. The increasing demand for such systems requires rationalization of the use of their expensive components, like noble metal catalysts. As such, a catalyst with low noble metal concentration, in which each one of the noble atoms is active, would reach the lowest price possible. Nevertheless, there are no reactivity descriptors outlined for this type of low coordinated supported atoms. Using DFT calculations, we consider three diverse systems as models of single atom catalysts. We investigate monomers and bimetallic dimers of Ru, Rh, Pd, Ir and Pt on MgO(001), Cu adatom on thin Mo(001)-supported films (NaF, MgO and ScN) and single Pt adatoms on oxidized graphene surfaces. Reactivity of these metal atoms was probed by CO. In each case we see the interaction through the donation-backdonation mechanism. In some cases the CO adsorption energies can be linked to the position of the d-band center and the charge of the adatom. Higher positioned d-band center and less charged supported single atoms bind CO weaker. Also, in some cases metal atoms less strongly bonded to the substrate bind CO more strongly. The results suggest that the identification of common activity descriptor(s) for single metal atoms on foreign supports is a difficult task with no unique solution. However, it is also suggested that the stability of adatoms and strong anchoring to the support are prerequisites for the application of descriptor-based search for novel single atom catalysts.

Single-atom catalysts (SACs) have attracted ever-growing interest due to their high atom-utilization efficiency and potential for cost-effective of hydrogen production. However, enhancing the hydrogen evolution reaction (HER) performance remains a key challenge in developing SACs for HER technology. Herein, we employed first-principles calculations in conjunction with the climbing-image nudged elastic band (CI-NEB) method to explore the effect of surface ligands (F, Cl, Br, I) on the HER performance and mechanism of single-atom (Pd or Cu)-anchored MoS2 monolayer. The results indicate that the relative Gibbs free energy for the adsorbed hydrogen atom in the I-Pd@MoS2 system is an exceptionally low value of -0.13 eV, which is not only comparable to that of Pt-based catalysts but also significantly more favorable than the calculated 0.84 eV for Pd@MoS2. However, the introduction of ligands to Cu@MoS2 deteriorates HER performance due to strong coupling between the absorbed H and ligands. It reveals that the ligand I restructures the local chemical microenvironment surrounding the SAC Pd, leading to impurity bands near the Fermi level that couple favorably with the s states of H atoms, yielding numerous highly active sites to enhance catalytic performance. Furthermore, the CI-NEB method elucidates that the enhanced HER mechanism for the I-Pd@MoS2 catalyst should belong to the coexistence of the Volmer-Tafel and Volmer-Heyrovsky reactions. This investigation provides a valuable framework for the experimental design and development of innovative single-atom catalysts.

The design of catalysts with desired chemical and thermal properties is viewed as a grand challenge for scientists and engineers. For operation at high temperatures, stability against structural transformations is a key requirement. Although doping has been found to impede degradation, the lack of atomistic understanding of the pertinent mechanism has hindered optimization. For example, porous gamma-Al2O3, a widely used catalyst and catalytic support, transforms to non-porous alpha-Al2O3 at ~1,100C. Doping with La raises the transformation temperature to ~1,250C, but it has not been possible to establish if La atoms enter the bulk, adsorb on surfaces as single atoms or clusters, or form surface compounds. Here, we use direct imaging by aberration-corrected Z-contrast scanning transmission electron microscopy coupled with extended X-ray absorption fine structure and first-principles calculations to demonstrate that, contrary to expectations, stabilization is achieved by isolated La atoms adsorbed on the surface. Strong binding and mutual repulsion of La atoms effectively pin the surface and inhibit both sintering and the transformation to alpha-Al2O3. The results provide the first guidelines for the choice of dopants to prevent thermal degradation of catalysts and other porous materials.

One of the great challenges facing atomically dispersed catalysts, including single-atom catalyst (SAC) and double-atom catalyst (DAC) is their ultra-low metal loading (typically less than 5 wt%), basically limiting the practical catalytic application, such as oxygen reduction reaction (ORR) crucial to hydrogen fuel cell and metal-air battery. Although some important progresses have been achieved on ultra-high-density (UHD) SACs, the reports on UHD-DACs with stable uniform dispersion is still lacking. Herein, based on the experimentally synthesized M2N6 motif (M = Sc-Zn), we theoretically demonstrated the existence of the UHD-DACs with the metal loading > 40 wt%, which were confirmed by systematic analysis of dynamic, thermal, mechanical, thermodynamic, and electrochemical stabilities. Furthermore, ORR activities of the UHD-DACs are comparable with or even better than those of the experimentally synthesized low-density (LD) counterparts, and the Fe2N6 and Co2N6 UHD-DACs locate at the peak of the activity volcano with ultra-low overpotentials of 0.31 and 0.33 V, respectively. Finally, spin magnetic moment of active center is found to be a catalytic descriptor for ORR on the DACs. Our work will stimulate the experimental exploration of the ultra-high-density DACs and provides the novel insight into the relationship between ORR activity of the DACs and their spin states.

Understanding how the local environment of a single-atom catalyst affects stability and reactivity remains a significant challenge. We present an in-depth study of Cu1, Ag1, Au1, Ni1, Pd1, Pt1, Rh1, and Ir1 species on Fe3O4(001); a model support where all metals occupy the same 2-fold coordinated adsorption site upon deposition at room temperature. Surface science techniques revealed that CO adsorption strength at single metal sites differs from the respective metal surfaces and supported clusters. Charge transfer into the support modifies the d-states of the metal atom and the strength of the metal-CO bond. These effects could strengthen the bond (as for Ag1-CO) or weaken it (as for Ni1-CO), but CO-induced structural distortions reduce adsorption energies from those expected based on electronic structure alone. The extent of the relaxations depends on the local geometry and could be predicted by analogy to coordination chemistry.

Redox and catalytic performance in total methane oxidation of a nonostructured ceria-terbia catalyst supported on magnesia is presented and compared to that of a pure ceria catalyst supported on MgO. The investigated material, Ce0.5Tb0.5Ox (3% mol.)/MgO, features several remarkable properties: a quite low total molar loading of the two lanthanide elements, high reducibility, as well as very high oxygen storage capacity al low temperatures and higher activity than MgO-supported ceria. In terms of lanthanide atomic content the catalytic performance of Ce0.5Tb0.5Ox (3% mol.)/MgO largely improves compared to that of bulk type ceria and ceria-magnesia solid solutions. Such a behavior implies proper optimization of the usage of lanthanide elements. A second contribution to atomic economy in the catalyst design relates to the fact that the new formulation demonstrate a stabilyty in the redox and catalytic performance against very high temperature treatments. An investigation on the structure of both the fresh and high-temperature-aged catalyst at the atomic scale by means of complementary aberration corrected microscopy techniques, reveals the ocuurrence of a variety of exotic, lanthanide-containing nanostructures, which span fron isolated, atomically dispersed Ln species to nonometer-sized CeTbO2-x patches, extended CeTbO2-x bilayers and 2D CeTbO2-x nanoparticles. Nanoanalytical results evidence the mixing of the two lanthanides at atomic levels in these nanostructures. The combined effects of nanostructuring, mixing of the lanthanides at the atomic level, and interaction with the MgO oxide are the roots of the improvement in funtional, redox and catalytic properties of the novel Ce0.5Tb0.5Ox (3% mol.)/MgO catalyst.

Electrochemical CO2 reduction (CO2R) offers a promising approach to decarbonize chemical manufacturing through production of carbon-neutral fuels. However, insufficient performance and instability of membrane electrode assembly (MEA) reactors limit commercial viability, with both metrics directly impacted by the CO2R catalysts. Here we develop an atomically dispersed nickel-nitrogen-carbon (Ni-NC) catalyst through a scalable synthesis approach using two different carbon supports. When using carbon nanotubes as the support, the resulting Ni-NCNT electrode achieves a partial current density toward CO of 558 mA cm-2 with 92 percent Faradaic efficiency toward CO at a cell voltage of 3.2 V and an energy efficiency of 39 percent toward CO at a total current density of 607 mA cm-2. The MEA demonstrates stable operation at 100 mA cm-2 over 210 hours, outperforming previously reported Ni-NC catalysts. Focused ion beam scanning electron microscopy (FIB-SEM) tomography illustrates the key role of catalyst support on the performance of the electrode. COMSOL Multiphysics simulations using 3D reconstructed images of the catalyst layers from FIB-SEM tomography demonstrate that the higher CO2R performance of the Ni-NCNT electrode is due to improved CO2 diffusion and a more uniform current-density distribution compared to the Ni-NCB electrode prepared with carbon black as the support. The stability and performance of the Ni-NCNT compare favorably to state-of-the-art Ag-based catalysts, while bottom-up cost analysis estimates the purchase cost of the Ni-NCNT catalyst to be about 589 USD per kg, substantially lower than the 1900 USD per kg estimated for Ag-based catalysts.

Single-atom catalysts are considered as a promising method for efficient energy conversion, owing to their advantages of high atom utilization and low catalyst cost. However, finding a stable two-dimensional structure and high hydrogen evolution reaction (HER) performance is a current research hotspot. Herein, based on the first-principles calculations, we identify the HER properties of six catalysts (TM@MoSi2N4, TM = Sc, Ti, V, Fe, Co, and Ni) comprising transition metal atoms anchored on MoSi2N4 monolayer. The results show that the spin-polarized states appear around the Fermi level after anchoring TM atoms. Therefore, the energy level of the first available unoccupied state for accommodating hydrogen drops, regulating the bonding strength of hydrogen. Thus, the single transition metal atom activates the active site of the MoSi2N4 inert base plane, becoming a quite suitable site for the HER. Based on ΔGH*, the exchange current density and volcano diagram of the corresponding catalytic system were also calculated. Among them, V@MoSi2N4 (ΔGH* = -0.07 eV) and Ni@MoSi2N4 (ΔGH* = 0.06 eV) systems show efficient the HER property. Our study confirms that the transition metal atom anchoring is an effective means to improve the performance of electrocatalysis, and TM@MoSi2N4 has practical application potential as a high efficiency HER electrocatalyst.

Single atoms and few-atom nanoclusters are of high interest in catalysis and plasmonics, but pathways for their fabrication and stable placement remain scarce. We report here the self-assembly of room-temperature-stable single indium (In) atoms and few-atom In clusters (2-6 atoms) that are anchored to substitutional silicon (Si) impurity atoms in suspended monolayer graphene membranes. Using atomically resolved scanning transmission electron microscopy (STEM), we find that the exact atomic arrangements of the In atoms depend strongly on the original coordination of the Si anchors in the graphene lattice: Single In atoms and In clusters with 3-fold symmetry readily form on 3-fold coordinated Si atoms, whereas 4-fold symmetric clusters are found attached to 4-fold coordinated Si atoms. All structures are produced by our fabrication route without the requirement for electron-beam induced materials modification. In turn, when activated by electron beam irradiation in the STEM, we observe in situ the formation, restructuring and translation dynamics of the Si-anchored In structures: Hexagon-centered 4-fold symmetric In clusters can (reversibly) transform into In chains or In dimers, whereas C-centered 3-fold symmetric In clusters can move along the zig-zag direction of the graphene lattice due to the migration of Si atoms during electron-beam irradiation, or transform to Si-anchored single In atoms. Our results provide a novel framework for the controlled self-assembly and heteroatomic anchoring of single atoms and few-atom clusters on graphene.

Developing single atom catalysts (SACs) for chemical reactions of vital importance in renewable energy sector has emerged as a need of the hour. In this perspective, transition metal based SACs with monolayer phosphorous (phosphorene) as the supporting material are scrutinized for their electrocatalytic activity towards oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) from first principle calculations. The detailed screening study has confirmed a breaking of scaling relationship between ORR/OER intermediates resulting in varied activity trends across the transition metal series. Group 9 and 10 transition metal based SACs are identified as potential catalyst candidates with platinum single atom offering bifunctional activity for OER and HER with diminished overpotentials. Ambient condition stability analysis of SACs confirmed a different extent of interaction towards oxygen and water compared to pristine phosphorene suggesting room for improving the stability of phosphorene via chemical functionalization.

Metal oxides have been extensively investigated and applied in environmental remediation and protection, energy conversion and storage. Most of these diverse applications are results of a large diversity of the electronic states of metal oxides. Noticeably, however, numerous metal oxides have obstacles for applications in catalysis because of low density of active sites in these materials. Size reduction of oxide catalyst is a strategy to improve the active site density. Here, we demonstrate the fabrication of single atomic metal oxide in which the oxide size reaches its minimum. However, the catalytic mechanism in this SATO is determined by a quasi atom physics which is fundamentally distinct from the traditional size effect, and also is in contrast to the standard condensed matter physics. SATO results in a record high and stable sunlight photocatalytic degradation rate of 0.24, which exceeds those of available photocatalysis by approximately two orders of magnitude. The photocatalytic process is enabled by a quasi atom physical mechanism, in which, an electron in the spin up channel is excited from HOMO to LUMO+1 state, which can only occur in SATO with W5+.

Polycrystalline boron-doped diamond (BDD) is widely used as a working electrode material in electrochemistry, and its properties, such as its stability, make it an appealing support material for nanostructures for electrocatalytic applications. Recent experiments have shown that electrodeposition can lead to the creation of stable small nanoclusters and even single metal adatoms on BDD surfaces. We investigate the adsorption energy and kinetic stability of single metal atoms adsorbed onto an atomistic model of BDD surfaces using density functional theory. The surface model is constructed using hybrid quantum/molecular mechanics embedding techniques and is based on an oxygen-terminated diamond (110) surface. We use the hybrid quantum mechanics/molecular mechanics method to assess the ability of different density-functional approximations to predict the adsorption structure, energy and the barrier for diffusion on pristine and defective surfaces. We find that surface defects (vacancies and surface dopants) strongly anchor metal adatoms on vacancy sites. We further investigate the thermal stability of metal adatoms, which reveals high barriers associated with lateral diffusion away from the vacancy site. The result provides an explanation for the high stability of experimentally imaged single metal adatoms on BDD and a starting point to investigate the early stages of nucleation during metal surface deposition.

The d-band center descriptor based on the adsorption strength of adsorbate has been widely used in understanding and predicting the catalytic activity in various metal catalysts. However, its applicability is unsure for the single-atom-anchored two-dimensional (2D) catalysts. Here, taking the hydrogen (H) adsorption on the single-atom-anchored 2D basal plane as example, we examine the influence of orbitals interaction on the bond strength of hydrogen adsorption. We find that the adsorption of H is formed mainly via the hybridization between the 1s orbital of H and the vertical dz2 orbital of anchored atoms. The other four projected d orbitals (dxy/dx2-y2, dxz/dyz) have no contribution to the H chemical bond. There is an explicit linear relation between the dz2-band center and the H bond strength. The dz2-band center is proposed as an activity descriptor for hydrogen evolution reaction (HER). We demonstrate that the dz2-band center is valid for the single-atom active sites on a single facet, such as the basal plane of 2D nanosheets. For the surface with multiple facets, such as the surface of three-dimensional (3D) polyhedral nanoparticles, the d-band center is more suitable.

Recent advances in nanomaterials have pushed the boundaries of nanoscale fabrication to the limit of single atoms (SAs), particularly in heterogeneous catalysis. Single atom catalysts (SACs), comprising minute amounts of transition metals dispersed on inert substrates, have emerged as prominent materials in this domain. However, overcoming the tendency of these SAs to cluster beyond cryogenic temperatures and precisely arranging them on surfaces pose significant challenges. Employing organic templates for orchestrating and modulating the activity of single atoms holds promise. Here, we introduce a novel single atom platform (SAP) wherein atoms are firmly anchored to specific coordination sites distributed along carbon-based polymers, synthesized via on-surface synthesis (OSS). These SAPs exhibit atomiclevel structural precision and stability, even at elevated temperatures. The asymmetry in the electronic states at the active sites anticipates the enhanced reactivity of these precisely defined reactive centers. Upon exposure to CO and CO2 gases at low temperatures, the SAP demonstrates excellent trapping capabilities. Fine-tuning the structure and properties of the coordination sites offers unparalleled flexibility in tailoring functionalities, thus opening avenues for previously untapped potential in catalytic applications.

Single-atom catalysts have attracted significant attention due to their exceptional atomic utilization and high efficiency in a range of catalytic reactions. However, these systems often face thermodynamic instability, leading to agglomeration under operational conditions. In this study, we investigate the interactions of twelve types of catalytic atoms (Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Ir, Pt, Au, and Bi) on three crystalline phases (1T, 1T', and 2H) of six transition metal dichalcogenide layers (MoS2, MoSe2, MoTe2, WS2, WSe2, and WTe2) based on first-principles calculations. We ultimately identify 82 stable single-atom systems that thermodynamically prevent the formation of metal clusters on these substrates. Notably, our findings reveal that the metastable 1T and 1T' phases significantly enhance the binding strength with single atoms and promote their thermodynamic stability. This research offers valuable insights into the design of stable single-atom systems and paves the way for discovering innovative catalysts in the future.

One-dimensional defects in graphene have strong influence on its physical properties, such as electrical charge transport and mechanical strength. With enhanced chemical reactivity, such defects may also allow us to selectively functionalize the material and systematically tune the properties of graphene. Here we demonstrate the selective deposition of metal at chemical vapour deposited graphene's line defects, notably grain boundaries, by atomic layer deposition. Atomic layer deposition allows us to deposit Pt predominantly on graphene's grain boundaries, folds, and cracks due to the enhanced chemical reactivity of these line defects, which is directly confirmed by transmission electron microscopy imaging. The selective functionalization of graphene defect sites, together with the nanowire morphology of deposited Pt, yields a superior platform for sensing applications. Using Pt-graphene hybrid structures, we demonstrate high-performance hydrogen gas sensors at room temperatures and show its advantages over other evaporative Pt deposition methods, in which Pt decorates graphene surface non-selectively.

The self-limiting nature of atomic layer deposition (ALD) makes it an appealing option for growing single layers of two-dimensional van der Waals (2D-VDW) materials. In this paper it is demonstrated that a single layer of a 2D-VDW form of SiO2 can be grown by ALD on Au and Pd polycrystalline foils and epitaxial films. The silica was deposited by two cycles of bis (diethylamino) silane and oxygen plasma exposure at 525 K. Initial deposition produced a three-dimensionally disordered silica layer; however, subsequent annealing above 950 K drove a structural rearrangement resulting in 2D-VDW; this annealing could be performed at ambient pressure. Surface spectra recorded after annealing indicated that the two ALD cycles yielded close to the silica coverage obtained for 2D-VDW silica prepared by precision SiO deposition in ultra-high vacuum. Analysis of ALD-grown 2D-VDW silica on a Pd(111) film revealed the co-existence of amorphous and incommensurate crystalline 2D phases. In contrast, ALD growth on Au(111) films produced predominantly the amorphous phase while SiO deposition in UHV led to only the crystalline phase, suggesting that the choice of Si source can enable phase control.

Despite its interest for CMOS applications, Atomic Layer Deposition (ALD) of GeO$_{2}$ thin films, by itself or in combination with SiO$_{2}$, has not been widely investigated yet. Here we report the ALD growth of SiO$_{2}$/GeO$_{2}$ multilayers on Silicon substrates using a so far unreported Ge precursor. The characterization of multilayers with various periodicities reveals successful layer-by-layer growth with electron density contrast and absence of chemical intermixing, down to a periodicity of 2 atomic layers.

The combination of h-BN and high-k dielectrics is required for a top gate insulator in miniaturized graphene field-effect transistors because of the low dielectric constant of h-BN. We investigated the deposition of Y2O3 on h-BN using atomic layer deposition. The deposition of Y2O3 on h-BN was confirmed without any buffer layer. An increase in the deposition temperature reduced the surface coverage. The deposition mechanism could be explained by the competition between the desorption and adsorption of the Y precursor on h-BN due to the polarization. Although a full surface coverage was difficult to achieve, the use of an oxidized metal seeding layer on h-BN resulted in a full surface coverage.

We report on growth of high-aspect-ratio ($\gtrsim300$) zinc sulfide nanotubes with variable, precisely tunable, wall thicknesses and tube diameters into highly ordered pores of anodic alumina templates by atomic layer deposition (ALD) at temperatures as low as 75 $^{\circ}$C. Various characterization techniques are employed to gain information on the composition, morphology, and crystal structure of the synthesized samples. Besides practical applications, the ALD-grown tubes could be envisaged as model systems for the study of a certain class of size-dependent quantum and classical phenomena.

Defect engineering enables hexagonal boron nitride (h-BN) to act as a platform for stabilizing isolated metal atoms, yet systematic identification of catalytically viable motifs remains limited. Here, density functional theory is used to screen transition and coinage metals anchored at B, N, and BN vacancies in h-BN for hydrogen evolution reaction (HER) activity. Cohesive-energy benchmarking reveals that B vacancies provide the strongest thermodynamic stabilization of single atoms, while electronic-structure analysis demonstrates vacancy-dependent modulation of conductivity and metal charge state. Hydrogen adsorption free energies identify Cu@VN and Pd@VB as near-thermoneutral candidates comparable to Pt(111). However, incorporation of electrochemical stability through Pourbaix analysis significantly refines this selection: Cu@VN is unstable at low pH and susceptible to OHads poisoning, whereas Pd@VB remains stable and catalytically accessible across a broad potential-pH range. These results show that descriptor-based HER screening can generate an expanded pool of candidates, but rigorous electrochemical filtering is essential to identify truly robust systems. The presented multi-step strategy provides a general framework for rational discovery of single-atom catalysts on defect-engineered 2D supports.

Single-atom catalysts (SACs) maximize atom efficiency and exhibit unique electronic structures, yet realizing precise and scalable atomic dispersion remains a key challenge. Here, we report a non-equilibrium strategy for the scalable synthesis of SACs via ion implantation, enabling precise stabilization of metal atoms on diverse supports. Using an industrial-grade ion source, wafer-scale ion implantation with milliampere-level beam currents enables high-throughput fabrication of SACs, while the synergistic energy-mass effects stabilize isolated metal atoms in situ. A library of 36 SACs was constructed, and the resulting Pt/MoS2 exhibits outstanding hydrogen evolution performance with an overpotential of only 26 mV at 10 mA cm-2 and exceptional long-term stability, surpassing commercial Pt/C. This work demonstrates ion implantation as a versatile platform bridging fundamental SACs design and scalable manufacturing, providing new opportunities for high-performance catalysts in energy conversion applications.

In this work, we provide a computational methodological framework using the single-atom systems as an example material class for ammonia synthesis that is robust towards parameter selection. Applying this to Pt$_1$/g-C$_3$N$_4$, Ru$_1$/g-C$_3$N$_4$, and Fe$_1$/g-C$_3$N$_4$, we generate ensembles of limiting potentials, using the ensemble of functionals collected via Bayesian Error Estimation Functionals (BEEF), to robustly predict catalytic activity. We then extend this to study the scaling between NRR reaction intermediates and use it to identify that NNH* as the best descriptor for these relations. In addition, a procedure to investigate selectivity is outlined, and a more robust way to analyze the selectivity-activity trade-off is presented. For this single-atom material class, we find choosing catalysts that lie on the strong binding leg of the activity volcano are worth further exploration. Given the ease of integration of the proposed method with minimal additional computational cost, we believe this should become a routine part of analysis workflow for multi-electron electrochemical reactions.

Low‐temperature direct ammonia fuel cells (DAFCs) can be used for the on‐demand generation of clean electricity. However, such systems have low efficiency due to the kinetically sluggish ammonia oxidation reaction (AOR) and oxygen reduction reaction (ORR). Prior reports have largely focused on Pt‐based electrocatalysts, however, their high cost motivates the need for simultaneously increasing activity whilst reducing the metal loading. Here, the design of a bifunctional Pt single‐atom catalyst (SAC) is reported, with enhanced catalytic activities compared to commercial Pt/C for both reactions. Notably, by modulating the Pt SAC coordination, the optimal catalyst (Pt‐DG‐1) displayed a high AOR mass activity of 1.23 A mgPt−1 and ORR mass activity of 7.98 A mgPt−1. This is then integrated into a DAFC as both the cathode and anode, achieving a peak power density of 21.8 mW cm−2 and low Pt mass loading of only 0.034 mg cm−2. In situ shell‐isolated nanoparticle‐enhanced Raman spectroscopy (SHINERS) experiments on Pt‐DG‐1 indicate a lower *OH coverage under ORR conditions and suppressed formation of poisoning species *NOx under AOR conditions as additional reasons for its enhanced bifunctional catalytic activity. Importantly, the study demonstrates how SACs can be rationally designed for DAFC electrocatalysis.

Single atom catalyst, which contains isolated metal atoms singly dispersed on supports, has great potential for achieving high activity and selectivity in hetero-catalysis and electrocatalysis. However, the activity and stability of single atoms and their interaction with support still remains a mystery. Here we show a stable single atomic ruthenium catalyst anchoring on the surface of cobalt iron layered double hydroxides, which possesses a strong electronic coupling between ruthenium and layered double hydroxides. With 0.45 wt.% ruthenium loading, the catalyst exhibits outstanding activity with overpotential 198 mV at the current density of 10 mA cm−2 and a small Tafel slope of 39 mV dec−1 for oxygen evolution reaction. By using operando X-ray absorption spectroscopy, it is disclosed that the isolated single atom ruthenium was kept under the oxidation states of 4+ even at high overpotential due to synergetic electron coupling, which endow exceptional electrocatalytic activity and stability simultaneously. While water splitting offers a carbon-neutral means to store energy, water oxidation is sluggish and corrosive over earth-abundant electrocatalysts. Here, authors show single ruthenium atoms over cobalt-iron layered double hydroxides to be effective and stable oxygen evolution electrocatalysts.