光催化产氨中的氨再次分解

No abstract available

No abstract available

No abstract available

No abstract available

Engineering advantageous defects to construct well-defined active sites in catalysts is promising but challenging to achieve efficient photocatalytic NH3 synthesis from N2 and H2O due to the chemical inertness of N2 molecule. Here, we report defective Fe-based metal-organic framework (MOF) photocatalysts via a non-thermal plasma-assisted synthesis strategy, where their NH3 production capability is synergistically regulated by two types of defects, namely, bridging organic ligands and terminal inorganic ligands (OH- and H2O). Specially, the optimized MIL-100(Fe) catalysts, where there are only terminal inorganic ligand defects and coexistence of dual defects, exhibit the respective 1.7- and 7.7-fold activity enhancement comparable to the pristine catalyst under visible light irradiation. As revealed by experimental and theoretical calculation results, the dual defects in the catalyst induce the formation of abundant and highly accessible coordinatively unsaturated Fe active sites and synergistically optimize their geometric and electronic structures, which favors the injection of more d-orbital electrons in Fe sites into the N2 π* antibonding orbital to achieve N2 activation and the formation of a key intermediate *NNH in the reaction. This work provides a guidance on the rational design and accurate construction of porous catalysts with precise defective structures for high-performance activation of catalytic molecules.

No abstract available

Photocatalytic ammonia synthesis is a sustainable pathway to substitute the Haber-Bosch reaction where high energy consumption exists, and single-atom catalysts (SACs) are pivotal materials in this field rely on their...

Ammonia, a core raw material for the global agricultural and chemical industries, faces serious challenges in its conventional synthesis process (the Haber-Bosch method) due to its high energy consumption, high carbon emissions and dependence on fossil fuels. Photocatalytic ammonia synthesis technology provides a revolutionary solution for green ammonia economy by realizing efficient nitrogen reduction under mild conditions with solar energy as the driving force. In this study, we systematically review the mechanism of photocatalytic nitrogen reduction reaction, focusing on the adsorption activation of nitrogen molecules, electron transfer pathways, and intermediate product regulation strategies, and review multiple types of photocatalyst systems including metal oxides, sulfides, bismuth-based materials, and carbon-based materials. Modification strategies such as defect engineering, single-atom modification, heterojunction design and plasma effect can significantly optimize the light absorption range, suppress the carrier recombination and enhance the active site density. It is further pointed out that the existing catalytic systems still face bottlenecks such as low quantum efficiency, photocorrosion, and scale-up reactor design, and future studies are needed to promote the photocatalytic synthesis of ammonia from the laboratory to the industry through multiscale synergistic innovation. This study provides theoretical guidance and a practical framework for the design and development of an efficient and stable photocatalytic ammonia synthesis system, which is scientifically important for achieving the goal of carbon neutrality.

Ammonia (NH3), recognized as a prospective green energy carrier due to its high hydrogen density and ease of transport, has garnered significant attention. However, the conventional Haber–Bosch (H–B) process for ammonia synthesis necessitates high‐temperature and high‐pressure conditions, accompanied by substantial carbon dioxide emissions. Consequently, the development of novel green ammonia synthesis technologies has become a focal point of research. Photocatalytic ammonia synthesis, leveraging solar energy as the driving force, converts nitrogen to ammonia under ambient conditions, offering advantages such as low energy consumption and environmental friendliness. This review summarizes recent advancements in photocatalytic ammonia synthesis, emphasizing nitrogen activation mechanisms, photocatalytic reaction pathways, and the design and optimization strategies for various photocatalysts. Through a detailed analysis of biomimetic catalysts, Ti‐based materials, Bi‐based materials, metal–organic frameworks (MOFs) materials, graphitic carbon nitride (g‐C3N4) materials, and MXene materials, their applications and limitations in photocatalytic ammonia synthesis are discussed. Furthermore, this paper synthesizes photocatalyst design strategies, including morphology control, vacancy engineering, and bandgap engineering, aiming to provide theoretical support and practical guidance for the design of future novel photocatalysts.

No abstract available

The efficiency of photocatalytic ammonia (NH3) synthesis is severely limited by the extremely difficult activation of N2 owing to its high N≡N triple bond energy. To address this challenge, we propose an N-doping strategy to facilitate the N2 activation. Our strategy involves optimizing the electronic structure of the metal active sites by modulating the coordination element. First, we introduce five different N-coordination ligands with distinct steric hindrances and N electron densities (2-methylimidazole (MI), isoindolin-1-one (II), 1,2-benzisothiazolin-3-one (BIT), benzo[d]isoxazol-3-ol (BIX), and terephthalamide (TA)) into an amino-functionalized metal–organic framework (MOF), NH2-MIL-68 (NM), to construct the N-coordination via the partial replacement of the O-coordination in the metal clusters. Electrochemical impedance spectroscopy and photocurrent analysis demonstrate that N-doping enhances electron transfer and carrier separation. Moreover, incorporating ligands with moderate sizes and steric hindrances (II, BIT, and BIX) more effectively boosts the carrier separation efficiency than incorporating small (MI) or large (TA) ligands. Furthermore, the N-doped MOF modified with BIT (in which N exhibits a moderate electron density) exhibits the strongest carrier separation capability. Concurrently, the X-ray photoelectron spectroscopy, density functional theory, and N2 temperature-programmed desorption results confirm that the established low-electronegativity N-coordination elevates the electron density of the metal active sites, which consequently enhances the N2 activation process. The systematic optimization of the N-coordinating ligand species and doping concentrations allows the optimal NM-0.5BIT to achieve a NH3 production rate of 175.5 μmol/(g·h). The proposed N-doping strategy offers several insights into the activation of inert molecules and the development of organic framework photocatalysts.

Photocatalytic nitrogen reduction to ammonia (NH3) under ambient conditions offers a sustainable alternative to the energy-intensive Haber-Bosch process but faces significant challenges. Inspired by biological nitrogen fixation, a thiosalicylic acid (TSA)-derived Fe-S cluster catalyst with dual active sites (Fe4S4 and Fe2S2) is rationally designed and synthesized. Guided by the hard-soft acid-base (HSAB) theory, the Fe2⁺/Fe3⁺ ratio in the iron source is optimized to regulate the content of these two coordination structures in the catalysts. Experiments and theoretical calculations reveal that Fe4S4 exhibits strong N2 adsorption energy and enhances charge carrier mobility, while Fe2S2, with a higher d-band center, significantly reduces the reaction energy barrier and enhances the reducing capability. The synergistic effect of these dual Fe-S clusters endows the catalyst with exceptional photocatalytic performance, achieving a remarkable NH3 production rate of 1287.6 µmol h-1 g-1 under air without sacrificial agents. Moreover, the catalyst demonstrates practical applicability under natural sunlight with an NH3 yield of 220.6 µmol h-1 g-1, suggesting its potential as a solar-driven nitrogen fertilizer. This is further validated by its successful application in cultivating Scenedesmus obliquus, exhibiting efficient nitrogen resource utilization. This work not only advances bioinspired nitrogenase-mimicking catalyst design but also establishes a sustainable solar-to-chemical energy conversion pathway.

No abstract available

Photocatalytic conversion of N 2 to green NH 3 has become extremely promising as an alternative to the traditional Haber Bosch process for the resilient future. In this context, developing...

Lanthanide metals possess multiple oxidation states, being emerging as a frontier toward the nitrogen fixation, yet the knowledge regarding their photocatalytic mechanism and active sites is very limited. Herein, a...

No abstract available

No abstract available

No abstract available

Prospective photocatalytic ammonia synthesis process has received more attentions but quite challenging with the low visible light utilization and weak N2 molecule absorption ability around the photocatalysts. Herein, interface reconstruction of MXene-Ti3C2/CeO2 composites with high-concentration active sites through the carbon-doped process are presented firstly, and obvious transition zones with the three-phase reaction interface are formed in the as-prepared catalysts. The optimal co-doped sample demonstrates an excellent photo response in the visible light region, the strongest chemisorption activity and the most active sites. Moreover, much more in-situ extra oxygen defects are also produced under light irradiation. It is expected that the double decorated catalyst shows a remarked ammonia production rate of above 0.76 mmol gcal-1·h-1 under visible-light illumination and a higher apparent quantum efficiency of 1.08 % at 420 nm, which is one of the most completive properties for the photocatalytic N2 fixation at present.

Photocatalytic nitrogen reduction reaction (PNRR) is emerging as a sustainable ammonia synthesis approach to meet global carbon neutrality. Porous framework materials with well‐designed structures have great opportunities in PNRR; however, they suffer from unsatisfactory activity in the conventional gas‐in‐solvent system (GIS), owing to the hindrance of nitrogen utilization and strong competing hydrogen evolution caused by overwhelming solvent. In this study, porous framework materials are combined with a novel “solvent‐in‐gas” system, which can bring their superiority into full play. This system enables photocatalysts to directly operate in a gas‐dominated environment with a limited proton source uniformly suspended in it, achieving the accumulation of high‐concentrated nitrogen within porous framework while efficiently restricting the solvent‐photocatalyst contact. An over eightfold increase in ammonia production rate (1820.7 µmol g−1 h−1) compared with the conventional GIS and an apparent quantum efficiency as high as ≈0.5% at 400 nm are achieved. This system‐level strategy further finds applicability in photocatalytic CO2 reduction, featuring it as a staple for photosynthetic methodology.

Ammonia (NH3) decomposition to hydrogen (H2) offers a sustainable route for clean energy generation, benefiting from abundant feedstocks, ease of storage and zero-carbon cycle. Conventional NH3 decomposition, however, relies on Ru-based noble metal catalysts and requires temperatures above 400°C, resulting in high cost and limited scalability. The development of efficient, low-cost catalysts that operate under mild conditions is therefore imperative. Here, we report a novel Z-scheme photocatalyst composed of Co-doped CdS quantum dots anchored on NH2-MIL-53(Al) (Co-CdS QDs/MIL) via an interfacial N-Co-S single atom electron bridge (Co-SAEB). By precisely steering the separation and migration of photogenerated charges, this architecture drives efficient photocatalytic NH3 decomposition at ambient temperature. The catalyst achieves an exceptional H2 evolution rate of 18 µmol·g-1·s-1, surpassing existing photocatalytic systems and approaching the performance of photothermal NH3 decomposition processes. Combined characterization and theoretical analyses reveal that the Co-SAEB is pivotal in establishing a direct Z-scheme charge-transfer pathway, which suppresses carrier recombination and enhances both redox capability and photocatalytic durability. This work advances the fundamental understanding of Z-scheme electron transfer and provides a design strategy for highly active, stable and adaptable photocatalytic materials.

No abstract available

No abstract available

Dinitrogen (N2) is earth’s most abundant form of gas, and its photofixation into ammonia (NH3) is a sustainable solution. Solar-driven photoreduction of N2 to NH3 at ambient temperature and pressur...

No abstract available

Catalysts based on platinum group metals have been a major focus of the chemical industry for decades. We show that plasmonic photocatalysis can transform a thermally unreactive, earth-abundant transition metal into a catalytically active site under illumination. Fe active sites in a Cu-Fe antenna-reactor complex achieve efficiencies very similar to Ru for the photocatalytic decomposition of ammonia under ultrafast pulsed illumination. When illuminated with light-emitting diodes rather than lasers, the photocatalytic efficiencies remain comparable, even when the scale of reaction increases by nearly three orders of magnitude. This result demonstrates the potential for highly efficient, electrically driven production of hydrogen from an ammonia carrier with earth-abundant transition metals. Description Harnessing iron for photocatalysis Good catalysts bind substrates at intermediate strengths so that neither reactant binding nor product desorption limits the reaction. Platinum group metals often meet this criterion for many reactions and cannot be replaced with cheaper metals such as iron, which often oxidize under reaction conditions. Yuan et al. demonstrate ammonia decomposition to liberate hydrogen with a copper-iron photocatalyst in which plasmons excited in copper generate hot electrons that react with ammonia bound to iron. Iron is not a good thermal catalyst for this reaction, but photoinduced oxygen desorption makes it competitive with a similar copper–ruthenium photocatalyst and with ruthenium thermal catalysts. This reaction, which is driven with light-emitting diodes, may be competitive with thermal catalysts used in this hydrogen carrier system. —PDS Iron sites in a Cu-Fe antenna reactor complex achieve efficiencies similar to Ru for photocatalytic ammonia decomposition.

No abstract available

A noble-metal-free Ni-NC@TiO2 core-shell photocatalyst was developed for efficient hydrogen production from ammonia photodecomposition under visible light without the use of sacrificial agents. In this architecture, Ni nanoparticles are anchored on the nitrogen-doped carbon shell through strong Ni-N interfacial coordination. The conductive NC shell promotes the separation and transport of photogenerated charge carriers, while the Ni sites provide favourable centres for NH3 adsorption and dehydrogenation. Under visible-light irradiation, Ni-NC@TiO2 exhibits a hydrogen evolution rate approximately 43 times higher than that of pristine TiO2. Combined experimental characterizations and DFT calculations reveal that the interfacial Ni-N coupling not only accelerates carrier migration, but also modulates the electronic structure of the Ni sites, thereby lowering the reaction barrier for NH3 decomposition. Meanwhile, the catalyst shows excellent durability, maintaining stable activity over 40 h without detectable deactivation.

No abstract available

No abstract available

No abstract available

No abstract available

The essential role ammonia occupies, considering both its major industrial use for nitrogen‐rich fertilizers and the possibility of being utilized as medium for energy storage, clashes with the environmental drawbacks of the Haber‐Bosch process, its main production method. This review investigates the potential of photocatalytic nitrogen fixation (PNF) as an eco‐friendly approach, driven by solar energy and inspired by natural nitrogenase enzymes. It traces the historical development of nitrogen fixation methods and focuses on recent advancements in photocatalytic materials, including metal oxides, sulfides, and composite systems. Strategies to enhance catalytic performance ‐ including doping, defect engineering, and heterojunction construction – are showcased, thus providing a way to mitigate low conversion efficiency and electron‐hole recombination. The work concludes by presenting emergent materials that could revolutionize the field, offering new paths for sustainable ammonia production.

No abstract available

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.

No abstract available

No abstract available

Plasmonic photocatalysis aims to develop a highly reactive surface enriched with hot carriers to enable challenging chemical processes, including high-energy-barrier nitrogen reduction reactions. In traditional plasmonic photocatalysis, hot carriers often undergo rapid thermalization, leading to suboptimal catalytic efficiency. Moreover, the role of hot carriers in surface reactions is often complex and frequently overlooked. Here, we designed a photocatalyst through loading Au nanoparticles on Mo-doped W18O49 nanorods (Au-MWO-S) to achieve efficient nitrogen reduction to produce ammonia, with a formation rate reaching 571.0 µmol h-1 g-1 and solar-to-ammonia (STA) conversion efficiency up to 0.28%. It was revealed through in situ experiments and theoretical simulations that the shallow energy-level defects in MWO-S act as electron traps to rapidly capture, store, and release hot electrons, which greatly reduces the thermalization of hot electrons. At the same time, the local electromagnetic field of MWO-S was enhanced, creating a high-activity "hot" microenvironment on the surface of the photocatalyst. This, in turn, increased the occupancy of electrons in the anti-bonding orbitals of N2, significantly promoting photocatalytic nitrogen reduction reaction (pNRR). This work unveils the mechanism of hot carrier participation in surface reactions, inspiring the development of catalytic systems with hot-electron-active surfaces.

No abstract available

No abstract available

No abstract available

No abstract available

No abstract available

No abstract available

No abstract available

No abstract available

No abstract available

No abstract available

Photocatalytic nitrogen reduction (pNRR) offers a carbon-neutral route to ammonia by directly converting solar energy into chemical bonds, presenting a promising alternative to the energy-intensive Haber-Bosch process. However, current progress...

No abstract available

No abstract available

N2 reduction reaction (NRR) by light is an energy-saving and sustainable ammonia (NH3) synthesis technology. However, it faces significant challenges, including high energy barriers of N2 activation and unclear catalytic active sites. Herein, we propose a strategy of photo-driven ammonia synthesis via a proton-mediated photoelectrochemical device. We used redox-catalysis covalent organic framework (COF), with a redox site (-C=O) for H+ reversible storage and a catalytic site (porphyrin Au) for NRR. In the proton-mediated photoelectrochemical device, the COF can successfully store e- and H+ generated by hydrogen oxidation reaction, forming COF-H. Then, these stored e- and H+ can be used for photo-driven NRR (108.97 umol g-1) under low proton concentration promoted by the H-bond network formed between -OH in COF-H and N2 on Au, which enabled N2 hydrogenation and NH3 production, establishing basis for advancing artificial photosynthesis and enhancing ammonia synthesis technology.

No abstract available

Titanium dioxide-based photocatalysts have been used to perform the photo-oxidation of ammonium/ammonia to molecular nitrogen. Different light sources were employed, i.e., UV, LED visible light and natural sunlight, and their performance was compared in order to understand which setup was the most efficient. It was found that under selected conditions, the LED lamp, in combination with silver-promoted TiO2, was able to push the conversion of ammonium toward 48% after 4 h of reaction time. On the other hand, with a more powerful UV lamp, lower conversion was achieved, ca. 40%. Natural sunlight under the same conditions attained more than 38% conversion, but the fluctuation of the reaction conditions remain a very critical issue for the real exploitation of sunlight in water treatment.

No abstract available

No abstract available

To enhance the efficiency of SO4- based advanced oxidation processes (AOPs) in synergy with photocatalysis in eliminating contaminants, heterogeneous CuO-Co3O4 catalysts were synthesized by a co-precipitation method and evaluated in oxidizing ammonia (NH3). The removal of 96.1 % NH3 at room temperature was achieved in persulfate/photo-electrochemical catalysis (PEC/PS). The factors influencing NH3 removal include molar ratios of Cu/Co in CuO-Co3O4, external resistance and PS concentration. The activation of PS is affected by loading of metal oxides catalyst and its Cu/Co molar ratio (2 is optimal). On the catalyst surface, Co and Cu species were the primary reactive sites. The reaction mechanism involves the in-situ PS activation in synergy with PEC, accelerating the production of radical species, thereby enhancing ammonia oxidation and removal.

Advancing sustainable and clean energy technology is imperative in addressing the energy and environmental crisis. As an energy carrier, hydrogen has been getting attention due to its abundance, high energy density, and zero carbon emissions. Given the challenges associated with hydrogen storage and transportation, the oxidation of ammonia presents significant promise for renewable energy. Photoelectrochemical ammonia oxidation reactions (AOR) have garnered substantial interest, which demand active and stable photo-electrocatalyst. In this regard, we fabricated Ov-BiVO4/Ph-POP photoelectrodes by controlling the oxygen vacancies of pristine BiVO4 and depositing Ph-POP, a hydroxy-rich porous organic polymer, using a simple spray coating method. We conducted the AOR in both aqueous electrolytes and non-aqueous electrolytes like acetonitrile (CH3CN), resulting in improved photocurrents and enhanced stability compared to aqueous conditions for the cases of Ov-BiVO4 and Ov-BiVO4/Ph-POP. Importantly, Ov-BiVO4/Ph-POP demonstrated superior activity across all electrolyte solutions. This indicates that Ph-POP's capacity to enhance light absorption and provide adsorption sites for ammonia facilitates the oxidation reaction. These findings provide compelling evidence for the role of Ph-POP and pave the way for exploring the potential use of porous organic polymers in AOR.

While the catalyst development for emission control mostly starts at the powder level, structured coated catalysts are crucial for application. Hence, the transfer of manual catalysts preparation methods to robot-controlled processes is a key step toward reproducibility, scalability, and optimization, all needed in academia and industry. In this study, a laboratory-scale robot-controlled dip-coating device was developed and systematically evaluated for washcoating of monolithic honeycomb substrates. Parameters such as dwell time and dipping speed were independently varied. The washcoats were quantified using a photo-analysis method, providing descriptors such as open channel area and channel clogging. Using γ-Al2O3 as a model material, optimized robot-controlled parameters were identified. Next, 2 wt% Pt/Al2O3, 2 wt% Pt/TiO2, and 2 wt% Pt/CeO2 catalysts were automatically washcoated and compared to manually coated counterparts. The monolithic catalysts were evaluated in ammonia oxidation in an oxygen excess, with respect to NH₃ conversion and selectivity toward N2, N2O, and NOX. The results demonstrate that robot-controlled washcoating replicates key characteristics of manually prepared samples. Comparable open channel areas, catalyst loadings, and catalytic performances were achieved, particularly for Pt/Al2O3. While manual washcoating currently offers slightly finer control over coating thickness, the automated process provides significant advantages. The differences in activity and selectivity for Pt/TiO2 and Pt/CeO2 highlight the importance of further optimization for different support materials. Overall, this work establishes small scale robot-controlled washcoating as an alternative to manual methods, offering a platform for systematic catalyst optimization, including several catalyst layers and zone coatings.

No abstract available

No abstract available

No abstract available

No abstract available

The production of COx-free hydrogen via the ammonia decomposition reaction (ADR) using Fe-based non-precious metal catalysts has attracted much attention. N-H bond cleavage and N-N coupling are two key steps in NH3 decomposition, however, stronger Fe-N binding leads to iron catalysts typically exhibit lower activity. Herein, we develop FeCu alloy catalysts with optimized metal-nitrogen binding energy by incorporating Cu, a metal with inherently weaker nitrogen affinity, into Fe-based catalysts. The optimized Fe1Cu0.5/MgO catalyst exhibits remarkable catalytic performance, achieving an impressive H2 production rate of 139.1 mmol H2 gcat-1 h-1 at 550 °C under a high gas hourly space velocity (GHSV = 360,000 h-1). Mechanistic studies reveal that the modulation of the d-band structure due to the alloying effect optimizes the dissociation of NH3 and the binding ability of N* intermediates in the ADR process. Notably, in-situ X-ray absorption spectroscopy (XAS) combined with theoretical calculations confirm that FeCu alloying effectively reduces the N-N recombination energy barrier from 2.25 eV (Fe cluster) to 1.77 eV (FeCu cluster). These findings provide valuable insights for the rational design of highly active Fe-based catalysts for efficient ammonia decomposition and sustainable hydrogen production.

No abstract available

No abstract available

No abstract available

No abstract available

Ammonia decomposition has attracted significant attention in recent years due to its ability to produce hydrogen without emitting carbon dioxide and the ease of ammonia storage. This paper reviews the recent developments in ammonia decomposition technologies for hydrogen production, focusing on the latest advances in catalytic materials and catalyst design, as well as the research progress in the catalytic reaction mechanism. Additionally, the paper discusses the advantages and disadvantages of each method and the importance of finding non-precious metals to reduce costs and improve efficiency. Overall, this paper provides a valuable reference for further research on ammonia decomposition for hydrogen production.

No abstract available

No abstract available

No abstract available

Photo-thermal-coupling ammonia decomposition presents a promising strategy for utilizing the full-spectrum to address the H2 storage and transportation issues. Herein, we exhibit a photo-thermal-catalytic architecture by assembling gallium nitride nanowires-supported ruthenium nanoparticles on a silicon for extracting hydrogen from ammonia aqueous solution in a batch reactor with only sunlight input. The photoexcited charge carriers make a predomination contribution on H2 activity with the assistance of the photothermal effect. Upon concentrated light illumination, the architecture significantly reduces the activation energy barrier from 1.08 to 0.22 eV. As a result, a high turnover number of 3,400,750 is reported during 400 h of continuous light illumination, and the H2 activity per hour is nearly 1000 times higher than that under the pure thermo-catalytic conditions. The reaction mechanism is extensively studied by coordinating experiments, spectroscopic characterizations, and density functional theory calculation. Outdoor tests validate the viability of such a multifunctional architecture for ammonia decomposition toward H2 under natural sunlight. The author report a Ru NPs/GaN NWs nanoarchitecture on Si for utilizing full spectrum to drive efficient and robust photothermal H2 production from NH3 with a high turnover number of >3,400,750 over 400 h.

Photocatalytic ammonia decomposition offers a sustainable route for hydrogen production, but its development is limited by low catalytic efficiency and poorly understood mechanisms. Here, a protonated layered perovskite, HPrNb2O7 (HPNO), is reported as an efficient catalyst for ammonia decomposition under mild photo‐thermal conditions. Upon exposure to NH3 at elevated temperatures, HPNO promotes the in situ formation and intercalation of hydrazine intermediates within its interlayer galleries, enabled by thermally generated oxygen vacancies and hydrogen bonding. Advanced characterization techniques have been applied to confirm the formation and stabilization of hydrazine. It is also shown that thermal energy prolongs charge carrier lifetimes and enhances oxygen vacancy formation, contributing to a strong photo‐thermal synergy. The stabilization of hydrazine intermediate promotes the associative mechanism, lowering the activation barrier, thus leading to an enhanced hydrogen evolution rate of 1311.2 µmol·g−1·h−1 at 200 °C under simulated solar irradiation without any noble metal co‐catalyst. This work reveals a distinct, hydrazine‐mediated reaction pathway and positions layered protonated perovskites as promising materials for efficient, solar‐driven ammonia decomposition and sustainable hydrogen generation.

Ammonia is an alternative hydrogen storage material and a promising source of sustainable clean energy. The lack of a mechanistic understanding of ammonia electrooxidation hinders the efforts to overcome the slow kinetics of the anode reaction in direct ammonia fuel cells. Herein, we use surface-enhanced Raman spectroscopy to study the electro-decomposition of ammonia on the Au surface. We observe three key reaction intermediate species of *NH2, *NH and *NNH and thereby disclose a multistage interfacial decomposition mechanism. Among the three, detection of the N-coupled species fills the blank in the mechanistic study of ammonia oxidation. Additionally, we investigated the influence of the reactant concentrations on the different oxidation stages. This spectroscopic evidence opens up promising avenues to overcome the limitations associated with ammonia fuel cells.

Thermocatalytic ammonia decomposition for hydrogen production is regarded as an effective strategy to tackle the challenges of hydrogen storage and transport. Most current strategies focus on the adsorption-evolution mechanism to...

Driven by dual-carbon targets, marine engines are accelerating their transition towards low-carbon and zero-carbon. Ammonium–hydrogen fusion fuel is considered to be one of the most promising fuels for ship decarbonization. Using non-thermal plasma (NTP) catalytic ammonia on-line hydrogen production technology to achieve hydrogen supply is one of the most important means to guarantee the safety and effectiveness of hydrogen energy in the storage and transportation process. However, the efficiency of ammonia catalytic hydrogen production can be influenced to some extent by the presence of several factors, and the reaction mechanism is complex under the conditions of ship engine temperature emissions. This makes it difficult to realize the precise control of plasma catalytic hydrogen production from ammonia technology under temperature emission conditions, thus restricting an improvement in the ammonia conversion rate. In this study, a kinetic model of hydrogen production from ammonia catalyzed by NTP was established. The influencing factors (reaction temperature, pressure, N2/NH3 ratio in the feed gas) and mechanism path of hydrogen production from ammonia decomposition were explored. The results show that the increase in reaction temperature will lead to an increase in the ammonia conversion rate, while the ammonia conversion rate will decrease with the increase in reaction pressure and N2/NH3 ratio. When the reaction temperature is 300 K, the pressure is 1 bar, the feed gas is 98%N2/2%NH3, and the ammonia conversion rate is 16.7%. The reason why the addition of N2 is conducive to the hydrogen production from NH3 decomposition is that the reaction N2(A3) + NH3 => N2 + NH2 + H, triggered by the electron excited-state N2(A3), is the main reaction for NH3 decomposition.

Summary Nitrogen doped carbon materials have been studied as catalyst support for ammonia decomposition. There are 4 different types of nitrogen environments (graphitic, pyrrolic, pyridinic and nitrogen oxide) on the amorphous support identified. In this paper, we report a 5%Ru on MgCO3 pre-treated nitrogen doped carbon catalyst with high content of edge nitrogen-containing sites which displays an ammonia conversion rate of over 90% at 500°C and WHSV = 30,000 mL gcat−1 h−1. It also gives an impressive hydrogen production rate of 31.3 mmol/(min gcat) with low apparent activation energy of 43 kJ mol−1. Fundamental studies indicate that the distinct average Ru-N4 coordination site on edge regions is responsible for such high catalytic activity. Ammonia is stepwise decomposed via a Ru-N(H)-N(H)-Ru intermediate. This associative mechanism circumvents the direct cleavage of energetic surface nitrogen from metal to form N2 hence lowering the activation barrier for the decomposition over this catalyst.

No abstract available

This study investigated the ammonia decomposition mechanism over Ru/CeO2. Isotopic tests using ND3 revealed that the rate-determining step involves adsorbed nitrogen atoms on Ru. Moreover, an inverse kinetic isotope effect where ND3 decomposition was faster than NH3 was clearly observed. The origin of the inverse effect was explained by the lower D coverage on the catalyst surface compared to H coverage for mitigating the inhibition of ND3 activation.

Abstract Oxidation of ammonia (NH4+/NH3) from wastewater is a challenge due to its high stability and solubility in aqueous environments. A simple Ag2O/TiO2 (P25) catalyst was synthesized and used for photocatalytic oxidation of aqueous NH4+/NH3. Under UV illumination, the oxidation rate of NH4+/NH3 by 1% Ag2O/P25 is increased with increasing pHs, with a rate constant of 0.383 h−1 at pH 11.8. OH/h+ are important oxidative species that dominate the oxidation of NH4+/NH3. The respective contributions of Pathway I (the h+ mediated process) and Pathway II (the e− mediated process) are 66.2% and 33.8% to the oxidation of NH4+/NH3. Oxidation selectivity toward N2 is more favorable under high concentrations of NH4+/NH3 and low concentrations of Ag2O/P25. The improved separation of e−-h+ pairs on Ag2O/P25 facilitates generation of OH and h+, thus triggering the high conversion yield of NH4+/NH3. XPS analysis further suggests that Ag(I), instead of the photogenerated Ag(0), plays the predominant role in photocatalytic oxidation of NH4+/NH3. This work enriches our understanding on the photooxidation mechanism of NH4+/NH3 by Ag2O/P25.

Photocatalytic N2 fixation to NH3via defect creation on TiO2 to activate ultra-stable N <svg xmlns="http://www.w3.org/2000/svg" version="1.0" width="23.636364pt" height="16.000000pt" viewBox="0 0 23.636364 16.000000" preserveAspectRatio="xMidYMid meet"><metadata> Created by potrace 1.16, written by Peter Selinger 2001-2019 </metadata><g transform="translate(1.000000,15.000000) scale(0.015909,-0.015909)" fill="currentColor" stroke="none"><path d="M80 600 l0 -40 600 0 600 0 0 40 0 40 -600 0 -600 0 0 -40z M80 440 l0 -40 600 0 600 0 0 40 0 40 -600 0 -600 0 0 -40z M80 280 l0 -40 600 0 600 0 0 40 0 40 -600 0 -600 0 0 -40z"/></g></svg> N has drawn enormous scientific attention, but poor selectivity and low yield rate are the major bottlenecks. Additionally, whether N2 preferentially adsorbs on phase-selective defect sites on TiO2 in correlation with appropriate band alignment has yet to be explored. Herein, theoretical predictions reveal that the defect sites on disordered anatase (Ad) preferentially exhibit higher N2 adsorption ability with a reduced energy barrier for a potential-determining-step (*N2 to NNH*) than the disordered rutile (Rd) phase of TiO2. Motivated by theoretical simulations, we synthesize a phase-selective disordered-anatase/ordered-rutile TiO2 photocatalyst (Na-Ad/Ro) by sodium-amine treatment of P25-TiO2 under ambient conditions, which exhibits an efficient NH3 formation rate of 432 μmol g−1 h−1, which is superior to that of any other defect-rich disordered TiO2 under solar illumination with a high apparent quantum efficiency of 13.6% at 340 nm. The multi-synergistic effects including selective N2 chemisorption on the defect sites of Na-Ad with enhanced visible-light absorption, suitable band alignment, and rapid interfacial charge separation with Ro enable substantially enhanced N2 fixation.

Catalytic conversion of nitrate (NO3-) pollutants into ammonia (NH3) offers a sustainable and promising route for both wastewater treatment and NH3 synthesis. Alkali cations are prevalent in nitrate solutions, but their roles beyond charge balance in catalytic NO3- conversion have been generally ignored. Herein, we report the promotion effect of K+ cations in KNO3 solution for NO3- reduction over a TiO2-supported Ni single-atom catalyst (Ni1/TiO2). For photocatalytic NO3- reduction reaction, Ni1/TiO2 exhibited a 1.9-fold NH3 yield rate with nearly 100% selectivity in KNO3 solution relative to that in NaNO3 solution. Mechanistic studies reveal that the K+ cations from KNO3 gradually bonded with the surface of Ni1/TiO2, in situ forming a K-O-Ni moiety during reaction, whereas the Na+ ions were unable to interact with the catalyst in NaNO3 solution. The charge accumulation on the Ni sites induced by the incorporation of K atom promoted the adsorption and activation of NO3-. Furthermore, the K-O-Ni moiety facilitated the multiple proton-electron coupling of NO3- into NH3 by stabilizing the intermediates.

The limitation of inert N2 molecules with their high dissociation energy has ignited research interests in probing other nitrogen-containing species for ammonia synthesis. Nitrate ions, as an alternative feedstock with high solubility and proton affinity, can be facilely dissociated for sustainable ammonia production. Here we report a nitrate to ammonia photosynthesis route (NO3−RR) catalyzed by subnanometric alkaline-earth oxide clusters. The catalyst exhibits a high ammonia photosynthesis rate of 11.97 mol gmetal−1 h−1 (89.79 mmol gcat−1 h−1) with nearly 100% selectivity. A total ammonia yield of 0.78 mmol within 72 h is achieved, which exhibits a significant advantage in the area of photocatalytic NO3−RR. The investigation of the molecular-level reaction mechanism reveals that the unique active interface between the subnanometric clusters and TiO2 substrate is beneficial for the nitrate activation and dissociation, contributing to efficient and selective nitrate reduction for ammonia production with low energy input. The practical application of NO3−RR route in simulated wastewater is developed, which demonstrates great potential for its industrial application. These findings are of general knowledge for the functional development of clusters-based catalysts and could open up a path in the exploitation of advanced ammonia synthesis routes with low energy consumption and carbon emission. Photocatalytic reduction of waste nitrate offers an alternative route for ammonia production. Here the authors report BaO clusters on TiO2 for nitrate-ammonia photosynthesis with high ammonia yield.

The nitrogen (N2)‐to‐ammonia (NH3) fixation driven by renewable energy has an attractive prospect to relieve the global warming and reduce the consumption of fossil fuels. Ideally, photocatalytic, electrochemical, and photoelectrochemical approaches are developed as the next‐generation NH3 synthesis technologies to substitute the Haber–Bosch method. However, the NH3 yield rate of nitrogen reduction reaction (NRR) by green approaches is extremely low, resulting in the current dilemma of NRR and contamination issues. Thus, in this mini review, the past advances on the sustainable NRR are briefly summarized in the three aspects as follows: the selectivity and adjustment of various catalysts, the type of electrolyte/solvent system, and the investigation of reaction conditions. Subsequently, the recent critical activities in the area of sustainable NH3 synthesis are analyzed and discussed deeply, and a perspective for rational and healthy development of this area is provided positively.

We propose several superiorities of applying some particular metal sulfides to the photocatalytic nitrate reduction in aqueous solution, including the high density of photogenerated excitons, high N2 selectivity (without over-reduction to ammonia). Indeed, ZnCr2S4 behaved as a highly efficient photocatalyst and with the assistance of 1 wt% cocatalysts (RuOx, Ag, Au, Pd, or Pt), the efficiency was greatly improved. The simultaneous loading of Pt and Pd led to a synergistic effect. It offered the highest nitrate conversion rate of ~45 mg N/h together with the N2 selectivity of ~89%. Such a high activity remained steady after 5 cycles. The optimal apparent quantum yield at 380 nm was 15.46%. More importantly, with the assistance of the surface plasma resonance effect of Au, the visible light activity achieved 1.352 mg N/h under full arc Xe-lamp and 0.452 mg N/h under pure visible light (λ > 400 nm). Comparing to the previous achievements in photocatalytic nitrate removal, our work on ZnCr2S4 eliminates the over-reduction problem and possesses an extremely high and steady activity under UV-light, as well as a decent conversion rate under pure visible light.

The clean-energy-driven synthesis of urea from carbon- and nitrogen-containing small molecules has garnered significant interest but remained great challenges to achieve with high selectivity. Herein, we present a photocatalytic pathway for the selective urea synthesis through the oxidative coupling between CO and NH3. The key factor in this process is the atmospheric O2 level, which plays a crucial role in controlling both the urea production rate and its selectivity. Using oxygen-deficient TiO2 under an air-level (20%) O2 atmosphere, we achieved a urea generation rate of 54.31 mg gcat -1 h-1 with 100% selectivity. This rate is 38.52 times higher than under oxygen-free conditions, while further increasing the O2 level significantly reduces selectivity. Mechanistic studies reveal that the process begins with the oxidation of NH3 to •NH2 through oxidative radicals generated on TiO2, especially the oxygen-derived O2 •-. This •NH2 radicals then couple with CO to form urea. The concentration of radicals is controlled by the O2 level, with the optimal concentration under air-level O2 enabling efficient NH3 oxidation to •NH2 while preventing over-oxidation.

Photocatalytic nitrate (NO3 -) reduction to ammonia (NH3) presents a sustainable solution for simultaneous NH3 synthesis and wastewater remediation. However, achieving high selectivity is challenging, plagued by sluggish kinetics and parasitic side reactions. In this study, we rationally design a synergistic Ag-Cu dual-atom catalyst on g-C3N4 (AgCu-CN) that embodies a spatially decoupled tandem scheme. We demonstrate that the oxophilic Cu1 site serve as Lewis acid centers to efficiently capture and activate NO3 -, before the crucial *NO intermediate is shuttled to adjacent Ag1 site, which is intrinsically inert toward the hydrogen evolution reaction, act as dedicated hydrogenation center for rapid and deep *NO reduction. This atomic-level synergy manifests in a state-of-the-art performance, with AgCu-CN delivering an impressive 98% NH3 selectivity and a production rate of 630.5 µmol h-1 g-1 under visible light. In situ spectroscopic studies and theoretical calculations corroborate the tandem mechanism and the critical role of the Ag-Cu dual sites in steering reaction selectivity. This study establishes a powerful tandem catalytic design principle to manage the selectivity challenges in complex multi-proton/electron reactions.

The photocatalytic conversion of nitrogen into high-value ammonia products holds tremendous potential in the global nitrogen cycle. However, the activation of N2 and competition of hydrogen evolution limit the improvement of nitrogen fixation performance. In this study, we developed a fluorinated TiO2 (F-TiO2) using a hydrothermal-annealing method. The incorporation of F dopants not only enhances the adsorption and activation of N2 through electronic structure regulation, but also facilitates an in situ increase in active sites via the electron repulsion effect between F and Ti atoms. In addition, the presence of F on the surface effectively improved the nitrogen supply problem and optimized the nitrogen fixation selectivity for its hydrophobic modulation. The NH3 yield of the F-TiO2 photocatalyst reached 63.8 μmol h-1 g-1, which was 8.5 times higher than that of pure TiO2. And the selectivity experiment showed that the electronic ratio of NH3 to H2 production reached 0.890. This research offers valuable insights for the design of highly efficient and selective nitrogen-fixing photocatalysts.

With the development of industry, agriculture, and aquaculture, excessive ammonia nitrogen mainly involving ionic ammonia (NH4+) and molecular ammonia (NH3) has inevitable access to the aquatic environment, posing a severe threat to water safety. Photocatalytic technology shows great advantages for ammonia nitrogen removal, such as its efficiency, reusability, low cost, and environmental friendliness. In this study, CP (g-C3N4/CoP) composite materials, which exhibited high-efficiency ammonia nitrogen removal, were synthesized through a simple self-assembly method. For the optimal CP-10 (10% CoP) samples, the removal rate of ammonia nitrogen reached up to 94.8% within 80 min under visible light illumination. In addition, the nitrogen selectivity S(N2) is about 60% for all oxidative products. The high performance of the CP-10 photocatalysts can be ascribed to the effective separation and transmission of electron–hole pairs caused by their heterogeneous structure. This research has significance for the application of photocatalysis for the remediation of ammonia nitrogen wastewater.

Abstract Photocatalytic nitrogen fixation is considered as a promising strategy for ammonia production. In this study, non-metallic boron and noble metal silver modified graphitic carbon nitride were prepared by a direct in-situ decomposition-thermal polymerization method with dicyandiamide, boric acid and silver nitrate as the precursors. It was shown that Ag/B-doped g-C3N4 composites with optimal mass ratio exhibited improved photocatalytic ammonia production under simulated sunlight illumination by a factor of 5.5 and 1.5 times compared with the pristine g-C3N4 and B-doped g-C3N4, respectively. The superior photocatalytic property was attributed to the decreased band gap and formation of mesopores after boron doping, which enlarged the specific surface area and created abundant reactive sites on the g-C3N4 nanosheets. In addition, the loaded silver nanoparticles greatly inhibited the recombination of photogenerated charge carriers through heterojunction interface. This work provided new deep insights into the reasonable structure of g-C3N4 composite system for photocatalytic nitrogen fixation reactions.

ConspectusThe fixation of dinitrogen to ammonia is critically important for the biogeochemical cycle on earth. Ammonia also holds promise as a sustainable energy carrier. Tremendous effort has been devoted to the development of green processes and advanced materials for ammonia synthesis and decomposition under milder conditions, and encouraging progress has been made.The reduction of dinitrogen to ammonia needs electrons and protons, which hydridic hydrogen H- could supply. Polarized, electron-rich NxHy intermediates, on the other hand, can be stabilized by alkali or alkaline earth metal cations to lower kinetic barriers in the transformation. The inherent properties of alkali/alkaline earth metal hydrides (denoted as AH) endow them with a unique function in ammonia synthesis.In this Account, recent efforts in the exploration of alkali or alkaline earth metal hydrides (denoted as AH), amides, and imides (denoted as ANH hereafter) for ammonia synthesis and decomposition reactions will be summarized and discussed. We begin with an introduction to the chemistry of A with N2, NH3, and H2, highlighting the interconversion between AH and ANH that has profound implications on the formation and decomposition of NH3. We then present our finding on the strong synergistic effect between ANH and transition metals (TM) in ammonia decomposition catalysis, which stimulated our subsequent research on AH for ammonia synthesis. We discuss the effect and function mechanism of AH in the thermocatalytic and chemical looping ammonia synthesis processes. In the thermocatalytic process, AH cooperates with both early and late TM forming either composite catalysts with two active centers or complex metal hydride catalysts with electron- and hydrogen-rich ionic centers facilitating ammonia synthesis with high activities at lower temperatures. Very interestingly, AH levels the catalytic performances of TMs and intervenes in the energy-scaling relations of TM-only catalysts. Moreover, ANH serves as a new type nitrogen carrier effectively mediating ammonia synthesis via a low-temperature chemical looping process, in which N2 is fixed by AH forming ANH. Subsequently, ANH is hydrogenated to ammonia and AH. Late TMs have a strong catalytic effect on the chemical looping process. The unique interplay of A, N, TM, and H- offers plenty of opportunities for achieving dinitrogen conversion under mild conditions, while further efforts are needed to address the challenges in the fundamental understanding and practical application.

Abstract. Ammonia is emerging as a promising carbon-free hydrogen carrier due to its high hydrogen density, established distribution infrastructure, and potential role in facilitating a sustainable energy transition. The efficient catalytic decomposition of ammonia into hydrogen and nitrogen is important for utilizing its potential in low-carbon energy systems. This study synthesized and evaluated nickel catalysts supported on TiO2 (xNi/TiO2, where x = 5–20 wt%) for the thermal decomposition of ammonia. The catalytic activity, quantified as the percentage of hydrogen production from the outlet gas composition measured by gas chromatography based on ammonia decomposition stoichiometry, exhibited a significant correlation with Ni loading: TiO2 (13.42%), 5Ni/TiO2 (20.8%), 10Ni/TiO2 (31.1%), 15Ni/TiO2 (22.7%), and 20Ni/TiO2 (22.8%). Of the evaluated formulations, 10Ni/TiO2 exhibited the superior performance, underscoring an optimal dispersion–loading equilibrium for active site utilization. These findings emphasize the promise of Ni/TiO2 systems as abundant and economical catalysts for hydrogen production from ammonia. This study advances the objectives of ICCAS-2025 by showcasing catalytic materials that facilitate low-carbon initiatives and sustainable development via green hydrogen production.

Ammonia is used for global fertilizer production and is increasingly viewed as a viable carrier for renewable hydrogen and long-duration energy storage. Realizing this potential requires catalysts and process architectures that enable both N₂-to-NH₃ synthesis and NH₃-to-H₂ decomposition at substantially reduced temperature and pressure. This review surveys recent advances in which alkali- and alkaline-earth metal hydrides, amides, and imides act as dynamic redox and hydrogen/nitrogen-transfer media, undergoing reversible interconversion with N₂, H₂, and NH₃. We summarize thermocatalytic systems where hydridic H⁻ and electron-rich lattices promote N₂ activation, heterolytic H₂ cleavage, and N–H bond formation, including composite catalysts that exploit cooperative interfaces with transition metals and complex or mixed-anion hydrides that relax constraints imposed by conventional metal-only surfaces. We also discuss photo-assisted routes that leverage defect-stabilized charge carriers in hydrides to drive nitrogen conversion under illumination, and chemical-looping strategies that decouple nitrogen fixation from hydrogenation (or hydrogen release) to tune thermodynamics and mitigate competitive adsorption. Across these platforms, recurring motifs include lattice-mediated hydride/proton shuttling, interfacial electron donation, and reversible nitride–imide–amide formation that can be engineered to balance activity, selectivity, and stability. Finally, we outline key barriers to practical deployment, air/moisture sensitivity, carrier volatility, phase segregation, and limited operando understanding and highlight design priorities for stabilizing reactive phases and integrating reactors compatible with renewable heat, photons, or electricity, thereby enabling scalable and decentralized ammonia and hydrogen technologies.

No abstract available

An analytical equation for the rate of formation/consumption of nitrogen in the reversible reaction N2 + + 3H2 ↔ 2NH3 was obtained on the base of the analysis of the catalytic properties of 4%Ru–13.6%Cs/Sibunit and 4%Ru–5.4%Ba–7.9%Cs/Sibunit in the processes of ammonia decomposition (105 Pa; 350–470°C) and synthesis ammonia (6×105–5×106 Pa; 400–430°C). This equation allows one to describe correctly the dependence of the chemical reaction rate on the partial pressures of the components of the reaction mixtures for both forward and reverse reactions. The approach used to obtain the kinetic equation is based on the assumption that the adsorption sites on the ruthenium surface are initially filled with hydrogen and then replaced by nitrogen during competitive interaction. The values of the equilibrium constants and apparent activation energies for the synthesis and decomposition of ammonia on the 4%Ru–13.6%Cs/Sibunit and 4%Ru–5.4%Ba–7.9%Cs/Sibunit was found by using the proposed kinetic equation. The data are in good agreement with the ones presented in the literature.

Ammonia (NH3) synthesis from N2 via the Haber-Bosch (HB) process addressed the major challenge of finite fertilizer sources in the early 20th century,and today, it continues to sustain the human population of 8 billion.1 Furthermore, NH3 has been identified as a promising, carbon-free energy vector.2 However, HB operates at elevated temperatures and pressures in centralized facilities, accounting for 1.3% of carbon emissions.1 To decentralize and decarbonize NH3 synthesis, there is a need to develop a synthetic method that operates at ambient conditions. Methods for N2 fixation to NH3 at ambient conditions include via the nitrogenase enzyme, homogenous catalysts, and an electrochemical lithium-mediated process.1,3 Of these methods, the lithium-mediated process (Li-NRR) has demonstrated impressive gains in selectivity and stability, and it has been engineered into a continuous process.3 In Li-NRR, metallic Li is plated onto an electrode from a Li-containing salt dissolved in N2-saturated, organic solution. Electroplated lithium reacts with the saturated N2 to form surface lithium nitride (Li3N), and a proton donor, such as ethanol, provides protons to form NH3. Of note, a solid-electrolyte interphase (SEI) passivating layer forms at the Li-electrolyte interface from electrolyte decomposition products. The SEI layer moderates proton, Li+, and N2 transport, and therefore, its structure and composition have become a major focus of study.4 While much remains to be understood in the Li-NRR system, a broader question has been posed as to whether a non-Li material can mediate ammonia synthesis with a similar mechanism.5 Recently, our groups have demonstrated that Ca, the fifth most abundant element in the earth’s crust, can mediate nitrogen reduction to ammonia in a process henceforth referred to as calcium-mediated nitrogen reduction to ammonia (Ca-NRR).6 Inspired by recent advancements in Ca-metal batteries for Ca plating at room temperature, we have demonstrated that calcium tetrakis(hexafluoroisopropyloxy)borate (Ca[B(hfip)4]2) in tetrahydrofuran with ethanol can be used as the electrolyte to plate Ca and produce NH3. We hypothesized that Ca-NRR likely operates similarly to Li-NRR, where the SEI passivating layer plays a crucial role in the selective transport of species such as N2, protons, and Ca2+,6 however, much remains to be determined about the structure and composition of these interfaces. A useful method for understanding interfaces is neutron reflectometry. This technique involves the measurement of neutron reflectivity as a function of scattering vector that is fit to a model to determine the compositional and structural properties of a series of interfaces, i.e., scattering length density, thickness, and roughness of each layer.4 Neutron sensitivity to light-elements, e.g., H, and scattering contrast between isotopes, including H and D, enable tracking proton dynamics and incorporation into the layers. Of particular importance is the formation of a hydride which may lead to major side reactions, including the formation of H2. Herein, we measured the Ca-NRR system in-situ at varied applied current densities, and observed changes in layer properties. This technique, paired with ex-situ characterization, elucidates properties of the Ca-NRR plated and SEI passivation layers that can inform the rational, molecular design of nitrogen reduction systems. References Nørskov, J. et al. DOE Roundtable Report (2016). Chang, F. et al. Advanced Materials 33, 2005721 (2021). Fu, X. Pederson, J.B, Zhou, Y. et al. Science 379, 6633 707-712 (2023). Blair, S.J., Doucet, M. et al. Energy Environ. Sci., 16, 3391 (2023). Tort, R. et al. ACS Catalysis, 13, 22, 14513-14522 (2023). Fu, X., Niemann, V.A., Zhou, Y. et al. Nat. Mater. (2023).

Li-mediated ammonia synthesis is, thus far, the only electrochemical method for heterogeneous decentralized ammonia production. The unique selectivity of the solid electrode provides an alternative to one of the largest heterogeneous thermal catalytic processes. However, it is burdened with intrinsic energy losses, operating at a Li plating potential. In this work, we survey the periodic table to understand the fundamental features that make Li stand out. Through density functional theory calculations and experimentation on chemistries analogous to lithium (e.g., Na, Mg, Ca), we find that lithium is unique in several ways. It combines a stable nitride that readily decomposes to ammonia with an ideal solid electrolyte interphase, balancing reagents at the reactive interface. We propose descriptors based on simulated formation and binding energies of key intermediates and further on hard and soft acids and bases (HSAB principle) to generalize such features. The survey will help the community toward electrochemical systems beyond Li for nitrogen fixation.

Nonthermal plasma provides a unique environment for activating nitrogen molecules at low gas temperatures, offering new possibilities for ammonia synthesis beyond conventional thermal routes. However, the energy cost varies widely among different plasma devices, and the underlying controlling mechanisms remain unclear [1]–[2]. In this work, a comparative data-driven study is conducted to clarify how key non-equilibrium plasma characteristics influence both the production rate and the energy cost of ammonia synthesis in four typical atmospheric-pressure nonequilibrium plasma sources. Experimental datasets from gliding arc, microwave plasma, DBD, and APPJ are integrated into a machine learning regression framework to establish quantitative relationships between plasma temperature parameters and ammonia yield and energy cost. Feature analysis shows that vibrational excitation is the dominant reaction pathway in plasma-assisted ammonia synthesis. More than half of the variation in synthesis performance can be attributed to vibrational temperature in all four plasma systems. Electron energy distribution calculations confirm that, within a reduced electric field range of 20 to 100 Td, most electron energy is transferred into molecular vibrational excitation, establishing this pathway as the primary energy channel. Elevated electron temperature enhances electron impact excitation and dissociation, shifting the energy deposition toward high-energy channels, which weakens the selectivity for vibrational activation, particularly in gliding arc and microwave plasma systems. In contrast, rotational temperature primarily affects the reversibility of ammonia formation at elevated temperatures, where increased gas temperature promotes ammonia decomposition and accelerates vibrational relaxation. In addition, catalyst-assisted DBD systems exhibit substantially enhanced ammonia yield and reduced energy cost, highlighting the strong synergy between plasma activation and surface catalysis. These findings clarify the reaction mechanisms of plasma-assisted ammonia synthesis and provide guidance for reactor design and optimization.

No abstract available

No abstract available

Abstract Herein, 1T-phase MoS2 nanodots (NDs) anchored to g-C3N4 (1T-MoS2/g-C3N4) are firstly developed to operate as a highly efficient catalyst for electrochemical N2 fixation with superior selectivity. 1T-MoS2/g-C3N4 composite presents outstanding NRR performance with a FE of 20.48 % and a NH3 yield rate of 29.97 μg h−1 mg−1cat. at -0.3 V vs. RHE. Furthermore, 1T-MoS2/g-C3N4 composite also shows outstanding electrochemical stability and durability. 15N isotopic labeling experiment confirms that nitrogen in produced ammonia originates from N2 in electrolyte rather than the decomposition of g-C3N4. DFT calculations reveal the optimal reaction path of NRR with both associative distal and alternating pathways. This work may offer a hopeful lead for designing effective non-noble-metal NRR electrocatalysts.

No abstract available

Quantifying rates of nitrogen (N) fixation in complex biological systems is of specific and acute interest to a wide array of ecological, agricultural, and soil scientists. N-fixation assays are commonly achieved through incubation of the target system with N2 gas that is greatly enriched in the less abundant heavy isotope, 15N. However, contamination of 15N2 gas supplies with more biologically available N species, such as ammonia and nitrate/nitrite can profoundly interfere with such assays and lead to false positives and/or inflated estimates of N-fixation rates. Here, we identify the ongoing contamination of commercial 15N2 stocks and quantify the potential impact to organismal and soil N-fixation studies. Further, we provide recommendations for mitigating and correcting for the effects of contamination in gas stocks, and present a simple, rapid procedure for quantification utilizing the same instrumentation that is typically employed to analyse N isotope ratios in N-fixation studies.

The detection of ammonia in aqueous solutions using solid‐phase microextraction (SPME)‐GC‐MS (gas chromatography‐mass spectrometry) is described. This technique enables the direct detection of ammonia without the need for derivatization or the use of colorimetric methods, which can be prone to interference from transition metal ions or organic cosolvents typically used in nitrogen reduction catalysis. The use of a fused‐silica SPME fiber coated with polydimethylsiloxane/divinylbenzene is found to allow fast and direct quantification of ammonia with a limit of detection = 0.17 ppm and a limit of quantification = 0.5 ppm in water. The method is straightforward to implement and can be readily automated using commercial instrumentation. It is also capable of detecting isotopically labeled 15NH3 as well as simple alkylamines such as methylamine or ethylamine which may be produced or released during the course of a reaction.

Electrochemical nitrogen reduction under ambient conditions is constrained by the kinetic inertness of N2 and competition from the hydrogen evolution reaction. Here, we report an integrated plasma-electrolysis membrane-electrode assembly that couples a microstructured nonthermal surface discharge directly to a gas-diffusion cathode, enabling in situ generation and delivery of vibrationally excited N2, N2(ν), to the electrocatalytic interface. Among 14 metal catalysts screened, Ag provided the best balance of activity and selectivity, achieving an NH3 production rate of 7.7 ± 0.8 nmol s-1 cm-2 with an electrochemical Faradaic efficiency of 86 ± 14% at -0.54 V versus RHE under atmospheric pressure and room temperature. Plasma/electrolysis on-off controls and 15N2 isotope-labeling experiments establish that NH3 formation requires simultaneous plasma activation and electrochemical polarization and originates from the supplied N2. Plasma-kinetic modeling indicates strong vibrational excitation in the discharge, with a calculated effective vibrational temperature of approximately 4300 K and 11.8% of N2 occupying levels (ν = 4-8). Transport modeling further suggests that these comparatively long-lived excited states persist to the membrane-catalyst region. In situ Raman spectroscopy reveals N-N-containing surface intermediates only during coupled operation, while density functional theory shows that vibrational excitation lowers the free-energy requirement for the initial hydrogenation of N2 to *NNH and shifts the rate-determining step in a catalyst-dependent manner. These findings establish vibrational-state engineering as a strategy for coupling non-equilibrium molecular activation with electrocatalysis for distributed ammonia synthesis under ambient conditions.

Yield validation of dinitrogen reduction reaction (N2RR) catalysts with 15N isotope labeling experiments is frustrated by the high cost of 15N2 and the frequent occurrence of 15NH3 and 15NOx impurities in commercial 15N2 sources. Also, gas diffusion electrode (GDE) cell architectures are relevant to scaling N2RR but underexplored and limited by ex situ product analysis methods. To overcome these obstacles, we develop and demonstrate a protocol for N2RR catalyst testing using a scalable GDE cell architecture and specialized test station that facilitates in-line product analysis with multiturn time-of-flight mass spectrometry. This approach provides robust yield measurements through real-time monitoring of 15NH3 with ultrahigh mass resolution. The 15N-containing impurities are also monitored, allowing their influence to be mitigated. A minimum detectable yield of 6 pmol·cm–2·s–1 (at 2.00 sccm and utilizing a 5 cm2 electrode) for real-time 15NH3 yield rate measurements is achieved while using a cost-effective amount of 15N2 (<100 mL).

No abstract available

Unveiling the active phase of catalytic materials under reaction conditions is important for the designed construction of efficient electrocatalysts for selective nitrate reduction to ammonia. Here, we probed the origin of the prominent activity enhancement for CuO (Faradaic efficiency: 95.8%, Selectivity: 81.2%) toward selective nitrate electroreduction to ammonia. 15 N isotope labeling experiments proved that ammonia originated from nitrate reduction. Both the 1 H nuclear magnetic resonance (NMR) spectra and colorimetric methods were performed to quantify ammonia. In situ Raman and ex situ experiments revealed that CuO was electrochemically converted into Cu/Cu 2 O, which serves as an active phase. The combined results of online differential electrochemical mass spectrometry (DEMS) and density functional theory (DFT) calculations demonstrated that the electron transfer from Cu 2 O to Cu at the interface could facilitate the formation of * NOH intermediate and suppress the hydrogen evolution reaction, leading to high selectivity and Faradaic efficiency.

Developing highly active and stable nitrogen reduction reaction (NRR) catalysts for NH3 electrosynthesis remains challenging. Herein, an unusual NRR electrocatalyst is reported with a single Zn(I) site supported on hollow porous N‐doped carbon nanofibers (Zn1N–C). The Zn1N–C nanofibers exhibit an outstanding NRR activity with a high NH3 yield rate of ≈16.1 µg NH3 h−1 mgcat−1 at −0.3 V and Faradaic efficiency (FE) of 11.8% in alkaline media, surpassing other previously reported carbon‐based NRR electrocatalysts with transition metals atomically dispersed and nitrogen coordinated (TM‐Nx) sites. 15N2 isotope labeling experiments confirm that the feeding nitrogen gas is the only nitrogen source in the production of NH3. Structural characterization reveals that atomically dispersed Zn(I) sites with Zn–N4 moieties are likely the active sites, and the nearby graphitic N site synergistically facilitates the NRR process. In situ attenuated total reflectance‐Fourier transform infrared measurement and theoretical calculation elucidate that the formation of initial *NNH intermediate is the rate‐limiting step during the NH3 production. The graphitic N atoms adjacent to the tetracoordinate Zn–N4 moieties could significantly lower the energy barrier for this step to accelerate hydrogenation kinetics duing the NRR.

No abstract available