有机无机卤化物钙钛矿用于光催化反应

Molecular ferroelectrics have attracted extensive research interest due to their ferroelectric and piezoelectric properties, along with their tunable band structures, making them promising candidates for piezo-photocatalysis. However, the role of spontaneous polarization and piezoelectric fields in charge transfer remains insufficiently understood. In this study, we explored the ferroelectric organic-inorganic perovskite (4,4-difluorocyclohexylammonium)2PbI4 ((4,4-DFPD)2PbI4) as a piezo-photocatalyst in the HI splitting process for hydrogen production. Under combined ultrasonic and visible light irradiation, the hydrogen production rate of (4,4-DFPD)2PbI4 reached 1185.1 µmol·h-1·g-1, 1.95 times higher than under visible light alone and 12.1 times greater than that of the conventional MAPbI3 perovskite catalyst. Experimental and theoretical analyses reveal that the combination of light and pressure synergistically enhances charge separation and boosts catalytic efficiency, driven by built-in electric fields from spontaneous polarization, piezoelectric fields, and photoexcitation. This work provides valuable insights for the design of novel molecular ferroelectric catalysts with high efficiency for photocatalytic hydrogen evolution.

Halide perovskite has shown great potential in photocatalysis owing to its diversity, suitable energy band alignment, rapid charge transfer, and excellent optical properties. However, poor stability, especially under humid conditions, hinders their practical application in photocatalysis. In this work, we report the encapsulation of inorganic–organic hybrid perovskite QDs into MIL-101(Cr) through an in situ growth strategy to prepare a series of MAPbBr3@MIL-101(Cr) (MA = CH3NH3+) composites. The perovskite precursors, i.e., MABr and PbBr2, were successively introduced into the pores of MOF, where the perovskite quantum dots were self-assembled in the confined environment. In photocatalytic CO2 reduction, 11%MAPbBr3@MIL-101(Cr) composite displayed the best performance among the composites with a total CO and CH4 yield of 875 μmol g−1 in 9 h, which was 8 times higher than that of the pure MAPbBr3. Such high gas production efficiency could be maintained for 78 h at least without structural and morphologic decomposition. The remarkable stability and catalytic activity of composites are mainly due to the synergistic effect and improved electron transfer between MAPbBr3 and MIL-101(Cr). Moreover, these composites revealed a novel mechanism, showing switched CH4 selectivity with the controlling of the perovskite location and contents. Those with perovskites encapsulated in the mesopores of MIL-101(Cr) were more preferential for CO production, while those with perovskites encapsulated in both meso- and micropores could produce CH4 dominantly.

Despite intriguing optoelectronic attributes in solar cells, light-emitting diodes, and photocatalysis, the instability of organic-inorganic perovskites poises a grand challenge for long-term applications. Herein, we report a simple yet robust strategy via light-and-solution treatment to create an organic membrane that effectively passivates CH3NH3PbI3 (MAPbI3). Specifically, the restructuring of MA+ is observed on MAPbI3 in aqueous hydrogen iodide. HIO3 molecules are generated via the reaction between water and I2 induced by photocatalysis when MAPbI3 is illuminated. The hydrogen bonding between HIO3 molecules at different perovskite particles not only directs the creeplike growth of perovskite particles but also in situ forms a passivating layer firmly anchoring on the perovskite surface with hydrophilic -NH3+ groups tethering to perovskites and hydrophobic -CH3 moieties exposed to air. Intriguingly, such MA+ film greatly improves the stability of perovskites against moisture as well as their crystal quality, considerably enhancing the photocatalytic hydrogen evolution rate.

Cost-effective and efficient photocatalysis are highly desirable in chemical synthesis. Here we demonstrate that readily prepared suspensions of APbBr3 (A = Cs or methylammonium (MA)) type perovskite colloids (ca. 2-100 nm) can selectively photocatalyze carbon-carbon bond formation reactions, i.e., α-alkylations. Specifically, we demonstrate α-alkylation of aldehydes with a turnover number (TON) of over 52,000 under visible light illumination. Hybrid organic/inorganic perovskites are revolutionizing photovoltaic research and are now impacting other research fields, but their exploration in organic synthesis is rare. Our low-cost, easy-to-process, highly efficient and bandedge-tunable perovskite photocatalyst is expected to bring new insights in chemical synthesis.

Over the past few decades, organic–inorganic halide perovskites (OIHPs) as novel photocatalyst materials have attracted intensive attention for an impressive variety of photocatalytic applications due to their excellent photophysical (chemical) properties. Regarding practical application and future commercialization, the air–water stability and photocatalytic performance of OIHPs need to be further improved. Accordingly, studying modification strategies and interfacial interaction mechanisms is crucial. In this review, the current progress in the development and photocatalytic fundamentals of OIHPs is summarized. Furthermore, the structural modification strategies of OIHPs, including dimensionality control, heterojunction design, encapsulation techniques, and so on for the enhancement of charge‐carrier transfer and the enlargement of long‐term stability, are elucidated. Subsequently, the interfacial mechanisms and charge‐carrier dynamics of OIHPs during the photocatalytic process are systematically specified and classified via diverse photophysical and electrochemical characterization methods, such as time‐resolved photoluminescence measurements, ultrafast transient absorption spectroscopy, electrochemical impedance spectroscopy measurements, transient photocurrent densities, and so forth. Eventually, various photocatalytic applications of OIHPs, including hydrogen evolution, CO2 reduction, pollutant degradation, and photocatalytic conversion of organic matter.

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The designed synthesis of an S-scheme heterojunction has possessed a great potential for improving photocatalytic wastewater treatment by demostrating increased the photoredox capacity and improved the charge separation efficiency. Here, we introduce the fabrication of a heterojunction-based photocatalyst comprising bismuth oxychloride (BiOCl) and bismuth-based halide perovskite (BHP) nanosheets, derived from metal-organic frameworks (MOFs). Our composite photocatalyst is synthesized through a one-pot solvothermal strategy, where a halogenation process is applied to a bismuth-based metal-organic framework (CAU-17) as the precursor for bismuth sourcing. As a result, the rod-like structure of CAU-17 transforms into well-defined plate and nanosheet architectures after 4 and 8 h of solvothermal treatment, respectively. The modulation of the solvothermal reaction time facilitates the establishment of an S-scheme heterojunction, resulting in an increase in the photocatalytic degradation efficiency of rhodamine B (RhB) and sulfamethoxazole (SMX). The optimized BiOCl/BHP composite exhibits superior RhB and SMX degradation rates, achieving 99.8% degradation of RhB in 60 min and 75.1% degradation of SMX in 300 min. Also, the optimized BiOCl/BHP composite (CAU-17-st-8h sample) exhibited the highest rate constant (k = 3.48×10-3 min-1), nearly 6 times higher than that of the bare BHP in the photocatalytic degradation process of SMX. The enhanced photocatalytic efficiency can be endorsed to various factors: (i) the in-situ formation of two-components BiOCl/BHP photocatalyst, derived from CAU-17, effectively suppresses the aggregation of pristine BHP and BiOCl particles; (ii) the S-scheme heterostructure establishes a closely-knit interfacial connection, thereby facilitating efficient pathways for charge separation/transfer; and (iii) the BiOCl/BHP heterostructure enhances its capacity to absorb visible light. Our investigation establishes an effective strategy for constructing heterostructured photocatalysts, offering significant potential for application in photocatalytic wastewater treatment.

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In situ construction of metal halide perovskites (MHPs) based heterojunction via atom cosharing has been regarded as an effective strategy to improve the photocatalytic activities, due to the establishment of...

The sensitization of surface-anchored organic dyes on semiconductor nanocrystals through energy transfer mechanisms has received increasing attention owing to their potential applications in photodynamic therapy, photocatalysis, and photon upconversion. Here, we investigate the sensitization mechanisms through visible-light excitation of two nanohybrids based on CsPbBr3 perovskite nanocrystals (NC) functionalized with borondipyrromethene (BODIPY) dyes, specifically 8-(4-carboxyphenyl)-1,3,5,7-tetramethyl-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BDP) and 8-(4-carboxyphenyl)-2,6-diiodo-1,3,5,7-tetramethyl-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (I2-BDP), named as NC@BDP and NC@I2-BDP, respectively. The ability of I2-BDP dyes to extract hot hole carriers from the perovskite nanocrystals is comprehensively investigated by combining steady-state and time-resolved fluorescence as well as femtosecond transient absorption spectroscopy with spectroelectrochemistry and quantum chemical theoretical calculations, which together provide a complete overview of the phenomena that take place in the nanohybrid. Förster resonance energy transfer (FRET) dominates (82%) the photosensitization of the singlet excited state of BDP in the NC@BDP nanohybrid with a rate constant of 3.8 ± 0.2 × 1010 s–1, while charge transfer (64%) mediated by an ultrafast charge transfer rate constant of 1.00 ± 0.08 × 1012 s–1 from hot states and hole transfer from the band edge is found to be mainly responsible for the photosensitization of the triplet excited state of I2-BDP in the NC@I2-BDP nanohybrid. These findings suggest that the NC@I2-BDP nanohybrid is a unique energy transfer photocatalyst for oxidizing α-terpinene to ascaridole through singlet oxygen formation.

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Metal halide perovskite (MHP)‐based photocatalysts encounter significant stability challenges in water‐containing systems, posing a major obstacle to their application in artificial photosynthesis. Herein, an innovative and universal strategy is present to create MHP‐based ternary heterojunctions based on a self‐templating method. A series of composite catalysts featuring sandwich hollow structures are constructed, with MHPs such as CsPbBr3, Cs3Bi2I9, Cs3Sb2Br9, and Cs2AgBiBr6 serving as the intermediate layers. The unique sandwich structure effectively shields MHPs from direct water contact, allowing MHP‐based photocatalysts to exhibit exceptional stability in water‐containing photocatalytic environments for durations exceeding 200 h. Furthermore, the hollow design ensures complete contact between the reaction substrates with both the oxidation and reduction functional areas. Compared to single perovskite materials, MHP‐based ternary heterojunction photocatalysts exhibit stronger oxidation capability and improved charge separation efficiency, leading to a substantial enhancement in photocatalytic CO2 reduction performance. Notably, the ternary heterojunction with CsPbBr3 as the intermediate layer achieves an electron consumption rate of up to 1824 µmol g−1 h−1 for CO2 reduction, which is far superior to other reported MHP‐based catalysts under similar conditions. This study provides a potent strategy for simultaneously enhancing the stability and activity of MHP‐based photocatalysts, paving the way for their potential applications in artificial photosynthesis.

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Metal halide perovskites offer a promising opportunity for transforming solar energy into chemical energy, thereby addressing pressing environmental challenges. While their excellent optoelectronic properties have been successfully applied in photovoltaics, their potential in photocatalysis remains relatively unexplored. Herein, we report a novel humidity‐driven approach for the in situ synthesis of MAPbI3 nanocrystals (NCs) within a nickel acetate matrix, forming a nanocomposite thin film that enhances the system's stability and enables its use in photochemical reactions. UV‐Vis spectroscopy and X‐ray diffraction confirm the rapid and effective synthesis of NCs within the matrix after 1 min at 80% relative humidity (RH). Optimal photoconversion conditions are attained after 60 min of exposure at 80% RH, due to the increased porosity and nanocrystal size over time as revealed by electron microscopy. The MAPbI3‐Ni(AcO)2 nanocomposite exhibits superior photocatalytic activity compared to standard polycrystalline MAPbI3 films for the decomposition of Sudan III under simulated sunlight. Furthermore, the nanocomposite demonstrates good recyclability over multiple cycles. Overall, this work highlights the potential of MHP‐based nanocomposites for solar‐driven catalytic systems in pollution mitigation.

Organic-inorganic hybrid halide perovskites have emerged as promising photocatalysts for hydrogen production because of their high absorption coefficients and large carrier diffusion lengths. However, the synthesis and development of organic-inorganic perovskite bromide photocatalysts have not been fully explored. Herein, we report on a novel high-activity Bismuth (Bi) doped CH3NH3PbBr3 (MAPbBr3) photocatalyst that was successfully synthesized using the reverse-temperature crystallization method. This material exhibited a reduced band gap and increased free-carrier concentration compared to pure MAPbBr3. Molecular dynamics and lattice changes within the photocatalyst were systematically investigated using solid-state nuclear magnetic resonance spectroscopy (NMR). The photocatalyst employs hypophosphorous acid (H3PO2) as a stabilizer and platinum (Pt) as a co-catalyst in the photocatalytic hydrogen bromide (HBr) splitting system, achieving a hydrogen evolution rate of 3946.52 μmol·g-1·h-1 under visible light irradiation. Our experimental results suggest that the enhanced photocatalytic performance is attributed to Bi doping, which modifies the charge distribution in the region of the lead (Pb) octahedron, thereby promoting effective charge separation and improving the hydrogen production efficiency. This study provides new insights into the photocatalytic hydrogen production capabilities of organic-inorganic hybrid bromide perovskites.

The photocatalytic system using hydrohalic acid (HX) for hydrogen production is a promising strategy to generate clean and renewable fuels as well as value‐added chemicals (such as X2/X3−). However, it is still challenging to develop a visible‐light active and strong‐acid resistive photocatalyst. Hybrid perovskites have been recognized as a potential photocatalyst for photovoltaic HX splitting. Herein, a novel environmentally friendly mixed halide perovskite MA3Bi2Cl9–xIx with a bandgap funnel structure is developed, i.e., confirmed by energy dispersive X‐ray analysis and density functional theory calculations. Due to gradient neutral formation energy within iodine‐doped MA3Bi2Cl9, the concentration of iodide element decreases from the surface to the interior across the MA3Bi2Cl9–xIx perovskite. Because of the aligned energy levels of iodide/chloride‐mixed MA3Bi2Cl9–xIx, a graded bandgap funnel structure is therefore formed, leading to the promotion of photoinduced charge transfer from the interior to the surface for efficient photocatalytic redox reaction. As a result, the hydrogen generation rate of the optimized MA3Bi2Cl9–xIx is enhanced up to ≈341 ± 61.7 µmol h−1 with a Pt co‐catalyst under visible light irradiation.

It was thought that the organic-inorganic hybrid perovskite MAPbI3 could be used to collect visible light for the photocatalytic hydrogen evolution reaction (HER). However, its ability to generate H2 is limited. Herein, we synthesized amorphous NiCoB through a redox method and coupled it with MAPbI3 to form the NiCoB/MAPbI3 composite photocatalyst by electrostatic self-assembly. 30% NiCoB/MAPbI3 exhibited the maximum H2 generation yield of 2625.57 μmol g-1 h-1, which was approximately 114 fold that of pristine MAPbI3 and much better than that of Pt/MAPbI3. In addition to the excellent photocatalytic HER capability, NiCoB/MAPbI3 maintained good stability in the 24 h cycling hydrogen evolution experiment. The photoelectric analysis showed that NiCoB as a cocatalyst could realize rapid charge separation. This work can offer a reference for the construction of efficient photocatalysts based on lead halide perovskites.

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Lead halide perovskites have shown great potential in photovoltaic and photocatalytic fields. However, the toxicity of lead impedes their wide application. Herein composites of lead-free halide perovskite Cs2AgBiBr6 supported on nitrogen-doped carbon (N-C) materials were synthesized successfully through a facile one-pot method for the first time. Without deposition of noble metals as the cocatalyst, the optimal composite Cs2AgBiBr6/N-C (Cs2AgBiBr6/N-C-140) exhibits outstanding photocatalytic performance with a high hydrogen evolution rate of 380 μmol g-1 h-1 under visible light irradiation (λ ≥ 420 nm), which is about 19 times faster than that of pure Cs2AgBiBr6 and 4 times faster than that of physically mixed Cs2AgBiBr6/N-C-140, respectively. The Cs2AgBiBr6/N-C-140 composite also displays high stability with no significant decrease after six cycles of repeated hydrogen evolution experiments. The addition of N-C with a high surface area helps to prevent aggregation of Cs2AgBiBr6 NPs and provides more pathways for the migration of photoinduced carriers. The nitrogen dopant can facilitate photoinduced electron transfer from Cs2AgBiBr6 to N-C to result in spatially separated electrons and holes with prolonged electron time and greatly enhance the photocatalytic performance. This study indicates that Cs2AgBiBr6-based perovskite materials are promising candidates for photocatalytic hydrogen evolution.

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Lead‐free perovskites Cs3Bi2xSb2–2xI9 (x = 0.1, 0.3, 0.5, 0.7, 0.9) are prepared by a co‐precipitation method and their photocatalytic performance for hydrogen production is studied in aqueous HI solution. Compared with the lead‐based perovskite (CH3NH3)PbI3, Cs3Bi2xSb2–2xI9 has a better catalytic performance under air mass 1.5 G (AM 1.5 G) simulated sunlight (100 mW cm−2), powders of Cs3Bi0.6Sb1.4I9 (100 mg) loaded with Pt nanoparticles show < H2 evolution rate of 92.6 µmol h−1, which greatly exceeds that of (CH3NH3)PbI3 powders loaded with Pt nanoparticles (100 mg catalyst, 4 µmol h−1). The Cs3Bi2xSb2–2xI9 has a high stability, with no apparent decrease in catalytic activity after five consecutive H2 evolution experiments. The doping of Sb in Cs3Bi2xSb2–2xI9 effectively reduces the contribution of Bi3+ on the conduction band, attenuating the effect of Bi vacancy on band structure. Compared with pure Cs3Bi2I9 and Cs3Sb2I9, Cs3Bi2xSb2–2xI9 has fewer midgap states and better optical absorption, which greatly enhances its performance for the hydrogen evolution reaction.

Metal halide perovskites hold significant promise as photocatalysts for hydrogen evolution reaction. However, the low stability and insufficient exposure of active sites impair their catalytic efficiency. Herein, we utilized an extra-large-pore zeolite ZEO-1 as a host to confine and stabilize the CsPbBr3 nanocrystals for boosting hydrogen iodide splitting. The as-prepared CsPbBr3@ZEO-1 featured sufficiently exposed active sites, superior stability, along with extra-large pores of ZEO-1 that were favorable for adsorption and diffusion. Most importantly, the unique nanoconfinement effect of ZEO-1 led to the narrowing of the band gap of CsPbBr3, allowing for more efficient light utilization. As a result, the photocatalytic HER rate of the as-prepared CsPbBr3@ZEO-1 photocatalyst was increased to 1734 μmol·h-1·g-1, and the long-term stability. Furthermore, Pt was incorporated with well-dispersed CsPbBr3 nanocrystals into ZEO-1, resulting in a significant enhancement in activity. Further investigation revealed that the boosted photocatalytic performance of Pt/CsPbBr3@ZEO-1 could be attributed to the promotion of charge separation and transfer, as well as to the substantially lowered energy barrier for HER. This work highlights the advantage of extra-large-pore zeolites as the nanoscale platform to accommodate multiple photoactive components, opening up promising prospects in the design and exploitation of novel zeolite-confined photocatalysts for energy harvesting and storage.

Photocatalytic water splitting using semiconductors is a promising approach for converting solar energy to clean energy. However, challenges such as sluggish water oxidation kinetics and limited light absorption of photocatalyst cause low solar-to-hydrogen conversion efficiency (STH). Herein, we develop a photocatalytic overall water splitting system using I3-/I- as the shuttle redox couple to bridge the H2-producing half-reaction with the O2-producing half-reaction. The system uses the halide perovskite of benzylammonium lead iodide (PMA2PbI4, PMA = C6H5CH2NH2) loaded with MoS2 (PMA2PbI4/MoS2) as the H2 evolution photocatalyst, and the RuOx-loaded WO3 (WO3/RuOx) as the O2 evolution photocatalyst, achieving a H2/O2 production in stoichiometric ratio with an excellent STH of 2.07%. This work provides a detour route for photocatalytic water splitting with the help of I3-/I- shuttle redox couple in the halide perovskite HI splitting system and enlightens one to integrate and utilize multi catalytic strategies for solar-driven water splitting.

Photocatalytic hydrogen evolution (PHE) is attractive for sustainable energy production, yet its efficiency lags photovoltaic conversion mainly due to the step of H‒H bonding for hydrogen generation on photocatalysts. Herein, the spin-enhanced PHE using photocatalysts of chiral perovskites (MBPI) are reported, where the spin orientations of photocarriers are aligned antiparallelly for H‒H bonding via the chiral-induced spin selectivity (CISS) effect. It is observed that the rac-MBPI shows a 3.5-fold enhancement in PHE activity compared with R/S-MBPI under visible light illumination, which is related to the chiral distortions of octahedral units in perovskite structures. Structural distortions lead to the spin polarization of photogenerated carriers in chiral perovskites due to the CISS effect, as revealed by magneto-photocurrent measurements. Compared with the parallel spins in R/S-MBPI, the antiparallel spins in rac-MBPI are more favorable for the coupling of H* radicals, as proven by the electron paramagnetic resonance experiments. The spin-enhanced mechanism for PHE is universal for reduced dimensional (quasi-2D) chiral perovskites, and the H2 yield rate is optimized up to 0.61 mmol g-1 h-1 with an excellent stability over 100 hours.

To combat the energy crisis and environmental pollution, developing renewable energy technology such as hydrogen (H2) production is necessary. The sulfur–iodine thermochemical cycle has high commercial potential in conducting hydrogen iodide (HI) splitting for H2 generation, but it requires high‐temperature conditions. In comparison, photocatalytic HI splitting of halide perovskites is non‐polluted and low‐cost for H2 production at room temperature. Herein, an in situ constructed multidimensional bismuth (Bi)‐based 3D/2D EDABiI5/MA3Bi2I9 perovskite heterojunction is developed first by synergistically integrating dimensionality control with heterostructure engineering. Accordingly, the optimal EDABiI5/MA3Bi2I9 without any co‐catalysts exhibits the H2 evolution rate of 213.63 µmol h−1g−1 under irradiation. Equally importantly, interfacial dynamics of solid/solid and solid/liquid interfaces play a crucial role in photocatalytic performance. Therefore, using temperature‐dependent transient photoluminescence and electrochemical voltammetric techniques, it is confirmed that the exciton transportation of EDABiI5/MA3Bi2I9 is accelerated by stronger electronic coupling arising from an enhanced overlap of electronic wavefunctions. Moreover, the effective diffusion coefficient and electron transfer rate of EDABiI5/MA3Bi2I9 demonstrate efficient heterogeneous electron transfer, resulting in improved photocatalytic hydrogen production. Consequently, the in situ formation of perovskite heterostructures studied by a combination of photophysical and electrochemical techniques provides new insights into green hydrogen evolution and interfacial interaction dynamics for commercial applications of solar‐to‐fuel technology.

In spite of the key role of hydrogen bonding in the structural stabilization of the prototypic hybrid halide perovskite, CH3NH3PbI3 (MAPbI3), little progress has been made in our in-depth understanding of the hydrogen-bonding interaction between the MA+-ion and the iodide ions in the PbI6-octahedron network. Herein, we show that there exist two distinct types of the hydrogen-bonding interaction, naming α- and β-modes, in the tetragonal MAPbI3 on the basis of symmetry argument and density-functional theory calculations. The computed Kohn-Sham (K-S) energy difference between these two interaction modes is 45.14 meV per MA-site with the α-interaction mode being responsible for the stable hydrogen-bonding network. The computed bandgap (Eg) is also affected by the hydrogen-bonding mode, with Eg of the α-interaction mode (1.73 eV) being significantly narrower than that of the β-interaction mode (2.03 eV). We have further estimated the individual bonding strength for the ten relevant hydrogen bonds having a bond critical point.

Lead-halide perovskites have triggered the latest breakthrough in photovoltaic technology. Despite the great promise shown by these materials, their instability towards water even in the presence of low amounts of moisture makes them, a priori, unsuitable for their direct use as light harvesters in aqueous solution for the production of hydrogen through water splitting. Here, we present a simple method that enables their use in photoelectrocatalytic hydrogen evolution while immersed in an aqueous solution. Field’s metal, a fusible InBiSn alloy, is used to efficiently protect the perovskite from water while simultaneously allowing the photogenerated electrons to reach a Pt hydrogen evolution catalyst. A record photocurrent density of −9.8 mA cm−2 at 0 V versus RHE with an onset potential as positive as 0.95±0.03 V versus RHE is obtained. The photoelectrodes show remarkable stability retaining more than 80% of their initial photocurrent for ∼1 h under continuous illumination. Lead-halide perovskites are sensitive to humidity, which limits their use in water splitting applications. Here, the authors protect the perovskite layer with Field’s metal, driving photoelectrocatalytic hydrogen evolution in an aqueous solution for approximately one hour under constant illumination.

Imposing quantum confinement has the potential to significantly modulate both the structural and optical parameters of interest in many material systems. In this work, we investigate strongly confined ultrathin perovskite nanoplatelets APbBr3. We compare the all-inorganic and hybrid compositions with the A-sites cesium and formamidinium, respectively. Compared to each other and their bulk counterparts, the materials show significant differences in variable-temperature structural and optical evolution. We quantify and correlate structural asymmetry with the excitonic transition energy, spectral purity, and emission rate. Negative thermal expansion, structural and photoluminescence asymmetry, photoluminescence full width at half-maximum, and splitting between bright and dark excitonic levels are found to be reduced in the hybrid composition. This work provides composition- and structure-based mechanisms for engineering of the excitons in these materials.

Organolead halide perovskite photocathodes have shown great potential for photoelectrochemical hydrogen evolution due to their excellent solar-to-hydrogen conversion efficiency. However, the poor stability of perovskite in the aqueous environment and...

The structural stability of the extensively studied organic–inorganic hybrid methylammonium tetrel halide perovskite semiconductors, MATtX3 (MA = CH3NH3+; Tt = Ge, Sn, Pb; X = Cl, Br, I), arises as a result of non-covalent interactions between an organic cation (CH3NH3+) and an inorganic anion (TtX3−). However, the basic understanding of the underlying chemical bonding interactions in these systems that link the ionic moieties together in complex configurations is still limited. In this study, ion pair models constituting the organic and inorganic ions were regarded as the repeating units of periodic crystal systems and density functional theory simulations were performed to elucidate the nature of the non-covalent interactions between them. It is demonstrated that not only the charge-assisted N–H···X and C–H···X hydrogen bonds but also the C–N···X pnictogen bonds interact to stabilize the ion pairs and to define their geometries in the gas phase. Similar interactions are also responsible for the formation of crystalline MATtX3 in the low-temperature phase, some of which have been delineated in previous studies. In contrast, the Tt···X tetrel bonding interactions, which are hidden as coordinate bonds in the crystals, play a vital role in holding the inorganic anionic moieties (TtX3−) together. We have demonstrated that each Tt in each [CH3NH3+•TtX3−] ion pair has the capacity to donate three tetrel (σ-hole) bonds to the halides of three nearest neighbor TtX3− units, thus causing the emergence of an infinite array of 3D TtX64− octahedra in the crystalline phase. The TtX44− octahedra are corner-shared to form cage-like inorganic frameworks that host the organic cation, leading to the formation of functional tetrel halide perovskite materials that have outstanding optoelectronic properties in the solid state. We harnessed the results using the quantum theory of atoms in molecules, natural bond orbital, molecular electrostatic surface potential and independent gradient models to validate these conclusions.

Internal vibrations of organic cations in halide perovskites and their analogues could be used to study the crystal structure of these novel semiconductor materials. In this work, we have studied the vibration properties of the 3‐cyanopyridinium (3cp+ = [3‐CN‐C5H5NH]+) cation in the hybrid organic–inorganic halide post‐perovskite (3cp)PbBr3. For DFT modeling of the experimental Raman spectrum, we have constructed three different models: free cation, minimal stoichiometric cluster and nanocluster. Calculations of a free cation adequately describe most of the internal vibrations. To describe high‐wavenumber hydrogen stretching vibrations, and first of all N–H vibrations, it is necessary to use sufficiently large clusters. We show in the cluster approach for crystal field description that it is necessary to include in the cluster not only halogens but also their nearest environment. In this case, agreement with experiment is reached, and further considerations can be put forward about the strength of the hydrogen bond and its role in stabilising the crystal.

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Perfluorooctanoic acid-modified CsPbBr3 perovskite quantum dots (F-PQDs) are used as both luminescence centers and photocatalyst to prepare organic-inorganic nanohybrid assemblies. Polymerization-induced self-assembly (PISA) technology of poly(poly(ethylene glycol) monomethyl ether methacrylate)-b-poly(perfluorooctyl)ethyl...

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Using sunlight and water to get hydrogen (H2) offers a promising pathway toward a sustainable future. Severe recombination of photogenerated electron-hole pairs directly impedes photocatalytic H2 production, while the strong polarized field from ferroelectric materials has been demonstrated to effectively promote charge separation. However, several drawbacks still remain, such as low piezoelectric coefficient, difficulty in forming a polarized field, and complex calcination preparation process. Herein, we present an in situ heterogeneous nucleation crystallization strategy for organic-inorganic hybrid perovskite ferroelectrics, involving heterogeneous crystallization on the surface of solid photocatalyst, the emanation of a polarized field, and the enhancement of photocatalytic H2 production. Under the mechanical stimulus, a polarized field is generated with deformation of the molecular ferroelectrics, which reinforces the charge separation efficiency. Thus, photocatalytic H2 production increases to 6.725 mmol g-1 h-1, almost 26-fold compared to the control C3N4 catalyst (0.255 mmol g-1 h-1). Our work demonstrates the extensive application of molecular ferroelectrics for high performance photocatalyst design with enhanced photocharge separation.

S-scheme heterojunction photocatalyst MAPbI3@PCN-222 with light absorption extending to the NIR region is constructed by embedding organic-inorganic hybrid perovskite (MAPbI3) into porphyrinic Zr-MOF (PCN-222). Both in situ X-ray photoelectron spectroscopy, ultraviolet photoelectron spectral characterization, and photocatalytic polymerization experiment prove the formation of S-scheme heterojunction. MAPbI3@PCN-222 with a low dosage (90 ppm) displays an impressive photocatalytic ability for 980 nm light-mediated photoinduced electron/energy-transfer-reversible addition-fragmentation chain-transfer (PET-RAFT) polymerization in air. The well-defined controllable-molecular weight polymers including block copolymers and ultrahigh-molecular weight polymers can be achieved with narrow distributions (Mw/Mn < 1.20) via rapid photopolymerization. The industrial application potential of the photocatalyst also has been proved by scale-up synthesis of polymers with low polydispersity under NIR light-induced photopolymerization in a large-volume reaction system (200 mL) with high monomer conversion up to 99%. The penetration photopolymerization through the 5 mm polytetrafluoroethylene plate and excellent photocontrollable behavior illustrate the existence of long-term photogenerated electron transfer of heterojunction and abundant free radicals in photopolymerization. The photocatalyst still retains high catalytic activity after 10 cycles of photopolymerization in air. It is revealed for the first time that the special PET-RAFT polymerization pathway is initiated by the aldehyde-bearing α-aminoalkyl radical derived from the oxidization of triethanolamine (TEOA) by the heterojunction photocatalyst. This research offers a new insight into understanding the NIR-light-activated PET-RAFT polymerization mechanism in the presence of TEOA.

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Lead halide perovskite (LHP) nanocrystals have been actively pursued as catalysts in photocatalytic fields most recently, owing to their inexpensive fabrication techniques and excellent optoelectronic properties. However, LHP nanocrystals have never been used for artificial photosynthesis in aqueous solution due to their high sensitivity to water. Herein, for the first time, water-tolerant cobalt doped CsPbBr3/Cs4PbBr6 nanocrystals are successfully prepared with the protection of hexafluorobutyl methacrylate, which can be employed as efficient photocatalysts for visible-light-driven CO2 reduction in pure water. The perovskite nanocrystals with 2% cobalt doping exhibit impressive yield of 247 μmol g-1 for photocatalytic CO2 conversion to CO and CH4, using water as an electron source. Our study makes a great step for practical artificial photosynthesis using LHP nanocrystals as photocatalysts in aqueous solution.

A halide perovskite based photocatalyst has been demonstrated for the first time to simultaneously achieve efficient photocatalytic CO2 reduction and methanol oxidation, exhibiting an exciting yield of 1835 μmol g-1 for photocatalytic CO2-to-CO conversion. Moreover, almost stoichiometric value-added formic acid can be produced from methanol oxidation.

Developing strategies to optimize the reaction kinetics and promote the photocatalytic efficiency of metal halide perovskites represents a critical scientific challenge. The strain engineering emerges as an innovative approach to simultaneously regulate carrier dynamics and manipulate reaction intermediates/adsorbates via precise control of lattice distortion. Here, we synthesized a series of CsPb1-xCuxBr3 quantum dots (QDs) using a controlled hot-injection method. The ionic bonding characteristics and structural flexibility of CsPbBr3 enable precise lattice strain engineering via B-site cation substitution. This approach effectively modulates the electronic band structure through controlled distortion of [PbBr6]4- octahedra. The geometric phase analysis of high-resolution transmission electron microscopy images has demonstrated that Cu2+ incorporation induces compressive strain within the perovskite lattice. Meanwhile, density functional theory (DFT) calculations have confirmed that the d-band center shifts upward from -3.05 to -2.09 eV in the compressive-strained CsPb0.9Cu0.1Br3. Additionally, the fitting results of femtosecond transient absorption spectroscopy kinetics demonstrate that the shallow trap states formed by Cu-induced lattice distortion effectively steer photogenerated carriers toward interfacial redox processes, rather than bulk recombination. Consequently, it significantly enhances the separation of photogenerated electrons and holes, thereby optimizing the adsorption and desorption of key reaction intermediates during the CO2 photocatalytic reduction process. This research reveals the impact of strain engineering on photocatalytic CO2 reduction and provides theoretical guidance for designing high-performance photocatalytic materials.

Perovskite nanocrystals (PNCs) are of great interest for visible-light photocatalytic CO2 reduction because of their excellent optical and optoelectronic properties with suitable band positions. Given that such photophysical properties, as well as catalytic activity, are highly surface-dependent, PNC surfaces must be engineered to optimize all these aspects. Herein, a facile and effective method is introduced for enhancing the photocatalytic CO2 reduction performance of CsPbBr3 PNCs through interfacial reactions involving hydrobromic acid and oleylamine in water and hexane, respectively. The H+ ions supplied from the water phase protonate oleylamine to produce oleylammonium, and the supplied Br- ions fill the halide vacancies of the PNCs in hexane, which can be stabilized by oleylammonium passivation. Consequently, this process enables proton source generation and surface defect passivation in a single step, yielding PNCs with significantly enhanced photoluminescence quantum yields and photocatalytic CO2 reduction activity under visible-light irradiation. In situ diffuse-reflectance infrared Fourier-transform spectroscopy reveals that the enhanced photocatalytic activity arises from the reaction pathway involving oleylammonium as a proton source. This study demonstrates the potential of simple oil-water interface systems for PNC surface modification, offering a practical route to visible-light-driven energy conversion technologies.

Based on their excellent stability, high carrier mobility, and wide photoresponse range, composites formed by embedding perovskite quantum dots (PQDs) into metal-organic frameworks (PQDs@MOF) show great development potential in the field of photocatalysis, including the toxic hexavalent chromium (Cr6+) degradation, CO2 reduction, H2 production, etc. However, the rapid recombination of photogenerated carriers is still a major obstacle to the improvement of photocatalytic performance, and the internal mechanism of photocatalysis is still unclear. In this work, we construct a novel double heterojunction photocatalyst by encapsulating CsPbBr3 PQDs in Zr-based metal-organic frameworks (UiO-67) and loading additional hole-acceptor pentylenetetrazol (PTZ). Spontaneous photoinduced charge-transfer and separation between interfaces are confirmed by time-resolved photoluminescence and transient absorption spectroscopy. Furthermore, compared with pure UiO-67, the photoactivity of CsPbBr3 PQDs@UiO-67@PTZ increased 3-fold due to the long-lived charge-separated state. Our findings provide a new guideline for the design of PQDs@MOF-based photocatalysts with long-lived photogenerated carriers and outstanding photocatalytic activity.

Lead-free double perovskite Cs2AgBiBr6 (CABB) has emerged as a promising photocatalytic material, but its efficiency is limited by rapid electron-hole recombination and insufficient active sites. Herein, an S-scheme heterojunction photocatalyst was constructed through the in situ growth of CABB nanosheets on a zinc phthalocyanine (ZnPc) substrate, where ZnPc acted as the reduction site with abundant high-energy electrons. Comprehensive characterizations confirmed the formation of robust interfacial Zn-Br bonds, ensuring intimate contact between ZnPc and CABB. Under visible-light irradiation, the optimized 0.05ZnPc/CABB composite exhibited significantly enhanced photocatalytic activity, achieving complete degradation of Rhodamine B (RhB) within 20 min, which outperformed pristine CABB and ZnPc. Mechanistic investigations involving photoelectrochemical measurements and density functional theory calculations revealed that the S-scheme band alignment, driven by the interfacial Zn-Br bonds and the built-in electric field, significantly enhanced charge separation and transfer. Additionally, the composite displayed excellent stability, maintaining 99% RhB degradation efficiency after five cycles. This work provides a novel strategy to enhance CABB photocatalysis via constructing S-scheme heterojunctions with ZnPc, highlighting potential applications in environmental remediation.

Bi-based halide perovskites excel in photocatalysis due to low toxicity and high stability but face challenges like limited photo-generated carrier concentration and separation efficiency. Emerging halide perovskite heterojunctions improve carrier separation, yet their synthesis is complex, and reports regarding pollutant degradation are scarce. Here, we successfully construct and synthesize two-dimensional Cs2AgBiBr6/Cs3Bi2Br9/Cs2AgBiBr6 (CABB/CBB/CABB) sandwich heterojunction flakes using an antisolvent-mediated one-step rapid crystallization method, which realizes precise control of heterojunction area through stoichiometric ratio engineering. Tetracycline hydrochloride (TC-HCl) degradation under simulated sunlight irradiation is employed to evaluate the photocatalytic performance. Notably, the CABB/CBB/CABB (0.5) heterojunction achieves impressive photodegradation efficiency of 87.9% within 80 min, which is 1.74 and 1.42 times higher than that of CBB and CABB, respectively. The enhanced catalytic activity may be attributed to the synergistic effect of the extended absorption range caused by CABB and its unique twin S-scheme heterojunctions, which facilitate carrier generation and separation. Moreover, the in situ growth of CABB/CBB/CABB heterojunction offers a more efficient carrier separation path, thus achieving high photocatalytic efficiency. The proposed straightforward method for fabricating halide perovskite heterojunctions in this work provides a roadmap for the synthesis of perovskite heterojunctions and paves the way for their applications in high-efficiency photocatalysis and other fields.

Halide perovskite Cs3Bi2Br9 (CBB) has excellent potential in photocatalysis due to its promising light-harvesting properties. However, its photocatalytic performance might be limited due to the unfavorable charge carrier migration and water-induced properties, which limit the stability and photocatalytic performance. Therefore, we address this constraint in this work by synthesizing a stable halide perovskite heterojunction by introducing hydrogen titanate nanosheets (H2Ti3O7-NS, HTiO-NS). Optimizing the weight % (wt%) of CBB enables synthesizing the optimal CBB/HTiO-NS, CBHTNS heterostructure. The detailed morphology and structure characterization proved that the cubic shape of CBB is anchored on the HTiO-NS surface. The 30 wt% CBB/HTiO-NS-30 (CBHTNS-30) heterojunction showed the highest BnOH photooxidation performance with 98% conversion and 75% benzoic acid (BzA) selectivity at 2 h under blue light irradiation. Detailed optical and photoelectrochemical characterization showed that the incorporating CBB and HTiO-NS widened the range of the visible-light response and improved the ability to separate the photo-induced charge carriers. The presence of HTiO-NS has increased the oxidative properties, possibly by charge separation in the heterojunction, which facilitated the generation of superoxide and hydroxyl radicals. A possible reaction pathway for the photocatalytic oxidation of BnOH to BzH and BzA was also suggested. Furthermore, through scavenger experiments, we found that the photogenerated h+, e− and •O2− play an essential role in the BnOH photooxidation, while the •OH have a minor effect on the reaction. This work may provide a strategy for using HTiO-NS-based photocatalyst to enhance the charge carrier migration and photocatalytic performance of CBB.

We demonstrate appropriate tuning of heterojunctions in CsPbBrxCl3−x−MoS2 composites (where x=0,1,2,3) by controlled regulation of the halide stoichiometry in the perovskite. A thorough optimization procedure determined the most effective photocatalyst, considering the pristine MoS2, perovskites with varying halide ratios, various physical mixing ratios of the two, and in‐situ synthesized composite ratios of CsPbBrxCl3−x and MoS2 (2 : 1, 1.5 : 1, 1 : 1, 1 : 1.5, 1 : 2). Under two hours of exposure to visible light, a remarkable photocatalytic performance of CsPbBrCl2 : MoS2 with a 1 : 2 ratio was observed, removing 98 % of the methylene blue (MB) dye. Notably, only the CsPbBrCl2 and MoS2 composite demonstrated higher efficiencies since it resulted in a n‐n type II heterojunction. Additionally, the CsPbBrCl2 : MoS2 composite exhibits the highest reaction rate constant, fifteen times higher than the pristine perovskite. Reusability assessment of this combination revealed sustained activity of 87 % for up to 5 cycles. The hydrogen evolution reaction investigations were carried out using the optimized CsPbBrCl2 : MoS2 composite, which yielded 265 times more hydrogen than pristine CsPbBrCl2. The Faradaic efficiency for 1 : 2 CsPbBrCl2 : MoS2 was found to be 96.61 %. Our results offer crucial perspectives on optimizing perovskite‐MoS2 composites and demonstrate their utility in sustainable applications, including water treatment, renewable energy harvesting, and environmental remediation.

The construction of efficient heterojunction photocatalysts critically relies on the precise regulation of interfacial charge dynamics. However, conventional heterojunctions are often constrained by rigid band alignments and sluggish interfacial charge transfer due to severe charge‐carrier recombination. Herein, we report a novel strategy for directional interfacial charge modulation through the construction of Cs2AgBiI6/Cu@ultrathin g‐C3N4 (CABI/Cu@UCN) heterojunction. Cu nanoclusters were anchored onto ultrathin g‐C3N4 via a hydrothermal–photoreduction process, forming Schottky junctions that functioned as efficient electron extractors. Subsequently, the lead‐free double perovskite Cs2AgBiI6 was coupled with Cu@UCN to construct a type‐II heterojunction. Owing to the synergistic driving force of interfacial built‐in electric fields, the distinctive “CABI→g‐C3N4→Cu” cascade charge‐transfer pathway enabled nearly dissipation‐free spatial separation efficiency of photogenerated electron–hole pairs. Under visible‐light irradiation, the optimized CABI/Cu@UCN composite exhibited outstanding photocatalytic activity and stability, achieving efficient degradation of various organic pollutants and antibiotics. The construction of the cascading heterogeneous structures facilitated the directional migration of electrons from CABI to UCN, and then to Cu, accompanied by significant interfacial charge redistribution. This work demonstrates that perovskite‐based heterostructures enable efficient photocatalytic degradation of dye and antibiotic pollutants through rational heterojunction design and interfacial charge regulation.

The application of halide perovskites in photocatalysis is severely limited by structural instability in polar solvents, such as dissolution and lattice degradation. Herein, we investigate the intrinsic stability in ethanol polar solvent of heterovalent metal cation‐substituted perovskite derivative Cs 2 AgBiBr 6 via density functional theory (DFT) calculations, exhibiting the suppressed ethanol‐induced bond relaxation with a smaller Cs‐Br bond length variation compared to that of CsPbBr 3 . Substantial interfacial electron transfer in CsPbBr 3 ‐ethanol promotes Pb‐Br bond dissociation, whereas Cs 2 AgBiBr 6 exhibits negligible electronic perturbation. Moreover, experimental evidences demonstrate better stability of Cs 2 AgBiBr 6 after long‐term exposing to ethanol, light, and Ar/air atmospheres. Based on this, we construct Cs 2 AgBiBr 6 /CdS heterojunction for photocatalytic ethanol dehydrogenation reaction. Through modification with Rh cocatalyst, which achieves a hydrogen evolution rate of 49.15 mmol·g −1 ·h −1 , AQY of 22.5%, and TOF of 197.5 h −1 over 60 h. At 60 °C, the ethanol dehydrogenation rate further increase to 277.35 mmol·g −1 ·h −1 and TOF of 1114.5 h −1 . Mechanistically, the Rh sites and heterojunction interface synergistically govern hydrogen evolution and ethanol oxidation pathways, facilitating C‐H/O‐H bond activation and regulating product selectivity. Our work not only provides new insights into perovskite stability but also expands their applicability in polar solvent‐based photocatalysis.

Metal halide perovskites (MHPs) with superior optoelectronic properties have recently been actively pursued as catalysts in heterogeneous photocatalysis. Dissociating excitons into charge carriers holds the key to enhancing the photocatalytic performance of MHP-based photocatalysts, especially for those with strong quantum-confinement effects. However, attaining efficient exciton dissociation has been rather challenging. Herein, we propose a novel concept that the edge interfacial state can trigger anisotropic electron transfer to promote exciton dissociation. By taking Cs4PbBr6/TiO2 mesocrystal heterojunction as a proof-of-concept, we demonstrate that the unique interfacial state at the edge of the system is generated by the defect-mediated chemical interaction and acts as a trap state, which brings on a directionally favored electron transfer from the center to edge regions, thereby significantly enhancing the desired exciton dissociation. Consequently, such a system achieves an excellent performance in photocatalytic CO2 reduction. This paradigmatic work sheds light on the excitonic aspects for rational design of advanced photocatalysts toward high performance.

Lead halide perovskites are promising for photocatalysis due to their excellent optoelectronic properties, high extinction coefficients, and long electron-hole diffusion lengths. However, severe recombination of photogenerated carriers limits their photocatalytic activity. Herein, we describe a perovskite-based step-scheme (S-scheme) heterojunction by interfacing CsPbBr3 perovskite nanocrystals with sulfur (S) doped graphitic carbon nitride (g-C3N4) ultrathin nanosheet. The formation of S-scheme heterojunction was substantiated by in-situ x-ray photoelectron spectra, showing a negative shift for Cs 1s, Pb 4f, and Br 3d binding energy in CsPbBr3, while a positive shift for C 1s, N 1s, and S 2p in S-doped g-C3N4 upon light irradiation. Moreover, alignment of Fermi levels in both semiconductors results in constructing a built-in electric field in the heterojunction, which enhances S-scheme electron transfer from g-C3N4 to CsPbBr3, favorable for electron (CsPbBr3) and hole (g-C3N4) separation for enhanced carbon dioxide (CO2) photoreduction. Indeed, compared with CsPbBr3, the developed CsPbBr3/S doped g-C3N4 composite showed a ∼16-fold improvement in the photocatalytic CO2 reduction rate (∼83.6 μmol h-1 g-1), thus holding great potential for photocatalysis applications in environmental and energy fields.

Very recently, halide perovskites, especially all-inorganic CsPbBr3, have received ever-increasing attention in photocatalysis owing to their superior optoelectronic properties and thermal stability. However, there is a lack of study on their application in thermocatalysis and photo-thermocatalysis. Herein, we rationally designed a core–shell heterojunction formed by encapsulating CsPbBr3 nanoparticles with the 2D C3N4 (m-CN) layer via a solid-state reaction (denoted as m-CN@CsPbBr3). A series of experiments suggest that abundant adsorption and active sites of CO2 molecules as well as polar surfaces were obtained by utilizing m-CN-coated CsPbBr3, resulting in significant improvement in CO2 capture and charge separation. It is found that the m-CN@CsPbBr3 effectively drives the thermocatalytic reduction of CO2 in H2O vapor. By coupling light into the system, the activity for CO2-to-CO reduction is further improved with a yield up to 42.8 μmol g−1 h−1 at 150 °C, which is 8.4 and 2.3 times those of pure photocatalysis (5.1 μmol g−1 h−1) and thermocatalysis (18.7 μmol g−1 h−1), respectively. This work expands the application of general halide perovskites and provides guidance for using perovskite-based catalysts for photo-assisted thermocatalytic CO2 reduction.

Due to their special physicochemical properties, organic-inorganic hybrid perovskite quantum dots (OIP QDs) are ideal and potential catalysts for the nitrogen reduction reaction (NRR). However, the OIP QD-based NRR is limited by poor water resistance, competitive suppression by the hydrogen evolution reaction, and inefficient active sites on the catalyst surfaces. Herein, to ensure an efficient NRR in aqueous solution, a water-resistant polycarbonate-part-encapsulated heterojunction of Zn,PtIV co-doped PbO-MAPbBr3 (PtIV/Zn/PbO/PC-Zn/MAPbBr3) is prepared through one-step electrospray-based microdroplet synthesis. Confirmed by both experimental and theoretical examinations, PbO is exposed on the PC-part-encapsulated surface to construct a Type I heterojunction. This heterojunction is further improved by synergistic co-doping with PtIV to facilitate efficient electron transfer for efficient photocatalysis of the NRR. Due to the active sites of the d-orbital electron-deficient Pt atoms (exhibiting a lower reaction energy barrier and highly selective N2 adsorption), the ammonia yield rate is 40 times higher than that without doping. This work initiates and develops on the application of OIP QDs in the NRR.

We report on theoretical investigations of a methylammonium lead halide perovskite system loaded with iron oxide and aluminum zinc oxide (ZnO:Al/MAPbI3/Fe2O3) as a potential photocatalyst. When excited with visible light, this heterostructure is demonstrated to achieve a high hydrogen production yield via a z-scheme photocatalysis mechanism. The Fe2O3: MAPbI3 heterojunction plays the role of an electron donor, favoring the hydrogen evolution reaction (HER), and the ZnO:Al compound acts as a shield against ions, preventing the surface degradation of MAPbI3 during the reaction, hence improving the charge transfer in the electrolyte. Moreover, our findings indicate that the ZnO:Al/MAPbI3 heterostructure effectively enhances electrons/holes separation and reduces their recombination, which drastically improves the photocatalytic activity. Based on our calculations, our heterostructure yields a high hydrogen production rate, estimated to be 265.05 μmol/g and 362.99 μmol/g, respectively, for a neutral pH and an acidic pH of 5. These theoretical yield values are very promising and provide interesting inputs for the development of stable halide perovskites known for their superlative photocatalytic properties.

ConspectusA persistent obstacle in heterogeneous photocatalysis is the rapid recombination of photogenerated electrons and holes, a consequence of the strong Coulombic attraction between carriers within conventional semiconductors. This intrinsic limitation significantly constrains the efficiency of solar-to-chemical conversion processes. Heterojunction engineering has therefore become a central strategy for promoting charge separation by coupling semiconductors with complementary electronic structures. Such systems typically outperform their single-component analogues because the interfacial electronic configuration promotes directional charge migration and suppresses bulk recombination losses.Within this context, S-scheme heterojunctions (SH) offer a mechanistically robust framework that reconciles efficient carrier separation with strong redox capability. An S-scheme couples a reduction photocatalyst (RP) and an oxidation photocatalyst (OP) in a staggered configuration. Under illumination, electrons in the OP selectively recombine with holes in the RP, while the high-energy electrons in the RP and high-energy holes in the OP are spatially retained and directed to catalytic sites. This selective recombination preserves redox power, enhances charge utilization, and accelerates surface reactions.Since introducing the S-scheme concept in 2019 with the WO3/g-C3N4 system supported by in situ irradiated X-ray photoelectron spectroscopy (ISIXPS)─we have expanded its material scope across multiple dimensional architectures, including perovskite materials, semiconducting quantum dots (QDs), conjugated polymers (CP), metal-organic frameworks (MOFs), and covalent-organic frameworks (COFs). To validate the S-scheme mechanism, elucidate charge transfer dynamics, and resolve reaction mechanisms, we have employed an array of state-of-the-art characterization techniques, such as light-irradiated Kelvin probe force microscopy (KPFM), in situ electron paramagnetic resonance (EPR), in situ X-ray absorption spectroscopy (XAS), and femtosecond-transient absorption spectroscopy (fs-TAS).Our most recent efforts focus on composition tuning, defect modulation, and interfacial bonding engineering to optimize the separation and lifetime of photogenerated carriers. Through these strategies, we aim to reinforce the internal electric field, regulate band bending, and precisely control charge flow pathways, ultimately maximizing photocatalytic efficiency. This Account provides a concise yet comprehensive overview of the evolution of SH, with emphasis on the design principles and advanced characterization techniques developed and adopted by our group. We summarize key strategies for engineering SH tailored for enhanced charge carrier separation and highlight their applications in major photocatalytic reactions. Finally, we outline promising future directions for the field.

Halide perovskites (HPs), renowned for their intriguing optoelectronic properties, such as robust light absorption coefficient, long charge transfer distance, and tunable band structure, have emerged as a focal point in the field of photocatalysis. However, the photocatalytic performance of HPs is still inhibited by rapid charge recombination, insufficient band potential energy, and limited number of surface active sites. To overcome these limitations, the integration of two-dimensional (2D) materials, characterized by shortened charge transfer pathways and expansive surface areas, into HP/2D heterostructures presents a promising avenue to achieve exceptional interfacial properties, including extensive light absorption, efficient charge separation and transfer, energetic redox capacity, and adjustable surface characteristics. Herein, a comprehensive review delving into fundamentals, interfacial engineering, and charge carrier dynamics of HP/2D material heterostructures is presented. Numerous HP/2D material photocatalysts fabricated through diverse strategies and interfacial architectures are systematically described and categorized. More importantly, the enhanced charge carrier dynamics and surface properties of the HP/2D material heterostructures are thoroughly investigated and discussed. Finally, an analysis of the challenges faced in the development of HP/2D photocatalysts, alongside insightful recommendations for potential strategies to overcome these barriers, is provided.

No abstract available

Solar-driven photocatalysis holds promise for fuel production, with halide perovskites leading owing to superior light absorption and carrier diffusion. However, precise control and understanding of interfacial charge separation dynamics in their heterostructures remain challenging. Using formamidinium lead bromide/molybdenum disulfide (FAPbBr3/MoS2) as a model, we engineered Pb-rich, Pb-neutral, and Pb-deficient surfaces via precursor stoichiometry tuning, modulating interface coupling through Pb-S bonds. High-density atomic bridging in Pb-rich interfaces boosts photogenerated charge separation efficiency from 29% to 63%, yielding a 98-fold hydrogen production increase and record 8.69% solar-to-hydrogen efficiency. Theoretical and experimental results demonstrate that the long carrier diffusion length and high photogenerated charge density of perovskites create a steep charge density gradient at the interface. This gradient directly induces a non-equilibrium internal electric field, which governs the charge transport dynamics. This work demonstrates the feasibility of sophisticated heterointerface tailoring and advances the understanding of the driving forces behind interfacial charge separation for perovskite photocatalysts.

Organic-inorganic hybrid perovskite materials show great potential in photocatalysis and solar cells due to their excellent photoelectric properties, while interface defects affect their photocatalytic performance and stability. In this study, machine learning techniques were used to perform preliminary screening and prediction of high-performance passivation molecules (PMs), and density functional theory was used to investigate the effect of PMs on interfacial passivation performance. It was found that the presence of different chemical bonds between PMs and the interface can significantly change the interface properties. Therefore, the effect of PMs on the performance of interfacial photocatalytic CO2 reduction reaction was explored. When PMs present N-Pb bonds at the interface, CO2 is reduced to CH3OH, while S-Pb bonds selectively generate CH2O from CO2, making perovskite selectively generate O-containing carbonyl compounds. The autocatalytic performance of organic compounds at the perovskite interface is poor and is not easy to occur. This study combines perovskite interface passivation and photocatalytic performance, providing a new approach for selective catalysis at perovskite interfaces.

Hybrid AMX3 perovskites (A=Cs, CH3NH3; M=Sn, Pb; X=halide) have in the last years revolutionized the scenario of photovoltaic technologies. Despite the extremely fast progress, the materials electronic properties which are key to the performance are relatively little understood. A series of computational simulation carried out using Car-Parrinello molecular dynamics have been performed investigating the nature of the perovskites/TiO2 interface, the role of moisture in the perovskite degradation process and the effect of the defect on the device working mechanism. Finally, a series of different strategies will be reported to increase the device stability and efficiency. While instability in aqueous environment has long impeded employment of metal halide perovskites for heterogeneous photocatalysis, recent reports have shown that some particular tin halide perovskites (THPs) can be water-stable and active in photocatalytic hydrogen production. To unravel the mechanistic details underlying the photocatalytic activity of THPs, we compare the reactivity of the water-stable and active DMASnBr3 (DMA = dimethylammonium) perovskite against prototypical MASnI3 and MASnBr3 compounds (MA = methylammonium), employing advanced electronic–structure calculations, see Figure 1. We find that the binding energy of electron polarons at the surface of THPs, driven by the conduction band energetics, is cardinal for photocatalytic hydrogen reduction. Figure 1

Two-dimensional (2D) lead halide perovskite nanoplatelets (NPLs) are promising materials for blue light emission because of the strong quantum confinement in the 2D morphology. However, the identity of carrier traps and the trap influence on charge transfer in these NPLs remain unclear. Herein, transient absorption studies revealed two types of electron traps in 3 monolayer lead bromide perovskite NPLs with trapping lifetime of 9.0 ± 0.6 and 516 ± 59 ps, respectively, while no hole traps were observed. Systematic charge transfer experiments show that electron traps have negligible influence on ultrafast electron transfer or hole transfer but extend the half-lifetime of the charge-separated state from 2.1 ± 0.1 to 68 ± 3 ns after hole transfer, which is explained by the reduced electron–hole overlap. This work contributes to the understanding of the fundamental carrier dynamics in 2D perovskite NPLs and offers guidelines for boosting their performance in optoelectronics and photocatalysis.

Advancing next-generation electrochemical systems for energy conversion requires a comprehensive understanding of the coupled processes of charge carrier generation, electron and ion transport, and interfacial electrochemical reactions. In this work, we integrate ab initio and machine learning-enhanced molecular dynamics simulations to investigate electrocatalytic water oxidation and selective species transport in photoelectrochemical and photocatalytic systems. For halide perovskite photoabsorbers with long carrier lifetimes, we demonstrate that spontaneous polarization domains and lattice dynamics govern charge separation and carrier dynamics. In colloidal suspension-type photocatalytic systems, we examine how the chemistry and geometry of protective oxide coatings influence the transport of reactants and redox shuttles through nanopores, revealing mechanisms of selective permeation that are potentially critical to Z-scheme photocatalysis. Furthermore, grand-canonical DFT simulations on IrO₂ surfaces under varying potentials reveal that surface hydrogen coverage directly modulates oxygen evolution reaction (OER) barriers and Tafel behavior. A continuum microkinetic model incorporating voltage-dependent surface coverage and active site accessibility successfully reproduces experimental current-voltage characteristics. Together, these findings highlight the synergistic effects of electrostatics, solvation, and surface chemistry on electrocatalytic performance, providing a rational framework for catalyst–overlayer interface design in water splitting and related reactions. This work was partially performed under the auspices of the U.S. DOE by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344 and supported by the U.S. DOE, Office of Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office as well as Office of Science, Basic Energy Science Program.

Crafting rational heterojunctions with nanostructured materials is instrumental in fostering effective interfacial charge separation and transport for optoelectronics. Layered halide perovskites (LHPs) that form heterojunctions between organic spacer molecules and inorganic metal halide layers exhibit tunable photophysics owing to their customizable band alignment. However, controlling photogenerated carrier dynamics by strategically designing layered perovskite heterojunctions remains largely unexplored. We combine a data-driven approach with time-domain density functional theory (TD-DFT) and non-adiabatic molecular dynamics (NAMD) to screen and select electronically active spacer dications (A') that introduce a type-II heterojunction in the lead iodide-based Dion-Jacobson phase LHPs. The composition-structure-electronic property correlations reveal that the number of nitrogens in aromatic heterocycles is the key factor in designing electron-accepting spacers in these perovskites. The detailed atomistic simulations validate the design strategy further by modeling (A')PbI4 perovskites, which incorporate three different screened electroactive A' spacers. The computed excited charge carrier dynamics illustrate the phonon-mediated ultrafast interfacial electron transfer from the inorganic conduction band edge to the lower-lying unoccupied orbitals of spacers, exhibiting photoluminescence quenching in these (A')PbI4 perovskites. The spatially separated electrons and holes at the type-II heterojunction interface prolong the excited charge carrier lifetime, boosting the carrier transport and exciton dynamics. Our work illustrates a robust in silico approach for designing LHPs with exciting optoelectronic properties originating from their fine-tuned heterojunctions.

Compositional engineering and doping of lead halide perovskites (LHPs) have emerged as promising methods to adjust the optical properties of these materials. Tin (Sn) doping, in particular, proves effective in achieving tunable band gaps, enhanced stability, high defect tolerance, and improved transport properties. However, the impact of tin doping on the photophysical properties of two-dimensional (2D) LHPs remains largely unexplored. This study investigates the optical properties, including excited state properties, of a Sn-doped 2D perovskite, utilizing various spectroscopic techniques. Our femtosecond transient absorption measurements reveal alterations in charge carrier dynamics within the 2D perovskite due to Sn doping. The doping leads to a significant reduction in charge carrier trapping, resulting in slower carrier recombination. Furthermore, Sn doping reduces the exciton binding energy, consequently decelerating exciton-exciton annihilation in the Sn-doped perovskite.

Lead halide perovskite and chalcogenide heterostructures which share the ionic and covalent interface bonding may be the possible materials in bringing phase stability to these emerging perovskite nanocrystals. However, in spite of significant successes in the development of halide perovskite nanocrystals, their epitaxial heterostructures with appropriate chalcogenide nanomaterials have largely remained unexplored. Keeping the importance of these materials in mind, herein, epitaxial nanocrystal heterostructures of CsPbBr3-PbSe are reported. The shape remained rhombic dodecahedral-tetrahedral, and the phase retained orthorhombic-cubic for CsPbBr3 and PbSe nanocrystals, respectively. These are synthesized following the standard classical approach of heteronucleations of chalcogenide PbSe with CsPbBr3 perovskite nanostructures and characterized with high-resolution electron microscopic imaging. With an ultrafast study, the hot charge transfer from CsPbBr3 to PbSe is also established. As these are first of its kind nanostructures which are obtained with heteronucleation and growth of chalcogenides on halide perovskites, this finding is expected to open the roadmap for designing other heterostructures which are important for catalysis and photovoltaic applications.

Because of the unique and superior optoelectronic properties, metal halide perovskites (MHPs) have attracted great interests in photocatalysis. Element doping strategy is adopted to modify perovskite materials to improve their photocatalytic performance. However, the contribution of bare doping-site onto photocatalytic efficiency, and the correlation between doping locations and activity have not yet to be demonstrated. This promoted us to explore the potential of A-site-doped MHPs for photocatalysis. Herein, we dope potassium (K+) into CsPbBr3 and first reveal that the occupied locations of K+ in CsPbBr3 is lattice incorporation rather than surface segregation, which would change from A-site substitution to interstitial site in lattice with the increase of K+ concentrations. Taking H2 evolution as a model reaction, photocatalytic activity of CsPbBr3 after K+ doping could be significantly improved ~11-fold with A-site substitution, which is superior to that of interstitial site doping. Moreover, other alkali metals including Li, Na, and Rb doping give the same results. The structure of photocatalysts during reaction confirmed the contribution of A-site doping onto enhanced photocatalytic activity. Mechanistic insights show it is a result of the relaxed residual lattice strain induced promoted charge-carriers dynamics and formed upward shifting of band after K+ A-site doping.

The development of water-stable Sn-based halide perovskites is highly desirable because of their promising applications in solar-driven photocatalysis and optoelectronics. However, given that Sn-based halide perovskites have only been discovered in recent years, the underlying mechanisms governing their stability in water and charge carrier dynamics are poorly understood. In this study, we have investigated the relationship between environmental stability and photochemical properties of DMASnI3 (DMA = CH3NH2CH3+) crystals in various solvents, including water. Our results reveal that exposure to specific polar solvents induced the formation of protective surface layers, leading to changes in the surface composition and optical properties, including a slight red-shift in the absorption edges. Time-resolved single-particle spectroscopy combined with in situ spectroelectrochemistry further demonstrated that exposure of DMASnI3 to water containing dissolved oxygen shifted the photoluminescence from green, likely originating from shallow trap states, to red, which is associated with deep trap states. These findings highlight the significance of local surface structures and environmental control in maintaining the structural integrity and photocatalytic performance of tin-based halide perovskites, contributing to developing robust lead-free materials for sustainable applications, such as hydrogen production and environmental remediation.

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