Tuning the Electronic Bandgap of Graphdiyne by H-Substitution to Promote Interfacial Charge Carrier Separation for Enhanced Photocatalytic Hydrogen Production

Graphdiyne (GDY), which features a highly π-conjugated structure, direct bandgap, and high charge carrier mobility, presents the major requirements for photocatalysis. Up to now, all photocatalytic studies are performed without paying too much attention on the GDY bandgap (1.1 eV at the G₀W₀ many-body theory level). Such a narrow bandgap is not suitable for the band alignment between GDY and other semiconductors, making it difficult to achieve efficient photogenerated charge carrier separation. Herein, for the first time, it is demonstrated that tuning the electronic bandgap of GDY via H-substitution (H-GDY) promotes interfacial charge separation and improves photocatalytic H₂ evolution. The H-GDY exhibits an increased bandgap energy ( ≈ 2.5 eV) and exploitable conduction band minimum and valence band maximum edges. As a representative semiconductor, TiO₂ is hybridized with both H-GDY and GDY to fabricate a heterojunction. Compared to the GDY/TiO₂, the H-GDY/TiO₂ heterojunction leads to a remarkable enhancement of the photocatalytic H₂ generation by 1.35 times under UV–visible illumination (6200 µ mol h⁻¹ g⁻¹) and four times under visible light (670 µ mol h⁻¹ g⁻¹). Such enhancement is attributed to the suitable band alignment between H-GDY and TiO₂, which efficiently promotes the photogenerated electron and hole separation, as supported by density functional theory calculations.     

Doped Mn Enhanced NiS Electrooxidation Performance of HMF into FDCA at Industrial-Level Current Density

Electrooxidation of 5-hydroxymethylfurfural (HMF) into 2,5-furandicarboxylic acid (FDCA) is a highly promising approach for producing value-added chemicals from biomass. However, developing highly efficient electrocatalysts for HMF oxidation (HMFOR) with high current density in large-scale productions remains a challenge. Herein, it is demonstrated that the Mn-doped NiS nanosheet electrocatalysts grown directly on 3D graphite felt (GF) substrates can efficiently perform electrooxidation of HMF into FDCA at industrial-level current density (500 mA cm⁻²) in the H-cell. The Mn_0.2NiS/GF exhibits excellent HMFOR performance with high selectivity (98.3%), yield (97.6%), faradaic efficiency (94.2%), and robust stability (10 cycles). Especially, FDCA production rate up to 4.56 g h⁻¹ can be achieved, superior to those reported in HMFOR literatures. Furthermore, by scaling up the Mn_0.2NiS/GF electrode area and assembling it in a continuous-flow electrolyzer, high FDCA production rate of 44.32 g h⁻¹ is achieved. The high activity of Mn_0.2NiS/GF for HMFOR can be attributed to incorporation of Mn into NiS material, theoretical calculation results indicate that the Mn and Ni as both the adsorption sites for HMF oxidation, thereby effectively facilitate the HMF electro-oxidation performance. This work provides a strategy for developing potential industrial-grade electrocatalysts at a large current density.     

Anisotropic Ag2S–Au Triangular Nanoprisms with Desired Configuration for Plasmonic Photocatalytic Hydrogen Generation in Visible/Near‐Infrared Region

Anisotropic Ag₂S‐edged Au‐triangular nanoprisms (TNPs) are constructed by controlling preferential overgrowth of Ag₂S as plasmonic photocatalysts for hydrogen generation. Under visible and near‐infrared light irradiation, Ag₂S‐edged Au‐TNPs exhibit almost fourfold higher efficiency (796 µmol h⁻¹ g⁻¹) than those of Ag₂S‐covered Au‐TNPs (216 µmol h⁻¹ g⁻¹) and pure Au‐TNPs in hydrogen generation. A single‐particle photoluminescence study demonstrates that the plasmon‐induced hot electrons transfer from Au‐TNPs to Ag₂S for hydrogen generation. Finite‐difference‐time‐domain simulations verify that the corners/edges of Au‐TNPs are high‐curvature sites with maximum electric field distributions facilitating hot electron generation and transfer. Therefore, Ag₂S‐edged Au‐TNPs are efficient plasmonic photocatalyst with the desired configurations for charge separation boosting hydrogen generation.     

Covalent Furan-Benzimidazole-Linked Polymer Hollow Fiber Membrane for Clean and Efficient Photosynthesis of Hydrogen Peroxide

Photocatalytic H₂O₂ production by conversion of O₂ in aqueous solution is often challenged by the use of sacrificial agents, the separation of powdery photocatalysts, solution, and contaminants, and low activity of photocatalyst. Herein, a membrane of covalent furan-benzimidazole-linked polymer (Furan-BILP) with both O- and N-containing heterocycles bonded via O C CN is reported for the first time as a photocatalyst to harvest clean H₂O₂ in pure water with high-performance. A coordination-polymer hard template strategy is developed to produce Furan-BILP hollow microfibers that can be further assembled into membranes with desired sizes. The resultant Furan-BILP membrane directly delivers clean H₂O₂ solution as the product with a high H₂O₂ production rate of 2200 µmol g⁻¹ h⁻¹ in pure water. Density functional theory calculations and experiment results indicate that the C atom from Furan ring on the linkage binds to the adsorbed OOH^*, the H atom of OOH^* forms a hydrogen bond with the N atom in the benzimidazole ring, thus the intermediate six-membered ring structure stabilizes the OOH^* and favors 2e-ORR. The strategy using both molecular engineering to tune the electronic structure and macrostructural engineering to shape the morphology may be applied to design other coordination organic polymer photocatalysts with further improved performance.     

Metastable Phase Cu with Optimized Local Electronic State for Efficient Electrocatalytic Production of Ammonia from Nitrate

Electrocatalytic nitrate (NO₃⁻) reduction reaction (NITRR) is an inspiring route for ammonia (NH₃) synthesis at ambient condition. The metallic Cu-based material with low cost and high activity is one of the most promising electrocatalysts for NITRR. However, due to the weaker atomic H^*-providing capacity, the produced intermediate—nitrite tends to accumulate on its surface, leading to unsatisfactory NH₃ selectivity and Faradic efficiency (FE). Herein, a novel and facile O₂/Ar plasma oxidation and subsequent electro-reduction strategy is developed to synthesize a kind of metastable phase Cu. Excitingly, the metastable phase Cu demonstrates superior NITRR performance to conventional phase Cu with high NH₄⁺ selectivity (97.8%) and FE (99.8%). Density function theory (DFT) calculations reveal that the upshift of the d-band center to near the Fermi level in metastable phase Cu contributes to the enhanced activity, while the relatively strong adsorption of H^* facilitates the conversion from NO₂^*/NO^* to NOOH^*/NOH^* and thus ensures high selectivity and FE. Furthermore, when evaluated as cathode material in Zn-NO₃⁻ battery, high power density (7.56 mW cm⁻²) and NH₄⁺ yield (76 µmol h⁻¹ cm⁻²) are achieved by the metastable phase Cu-based battery.     

Modular Type III Porous Liquids Based on Porous Organic Cage Microparticles

The dispersion of particulate porous solids in size-excluded liquids has emerged as a method to create Type III porous liquids, mostly using insoluble microporous materials such as metal–organic frameworks and zeolites. Here, the first examples of Type III porous liquids based on porous organic cages (POCs) are presented. By exploiting the solution processability of the POCs, racemic and quasiracemic cage microparticles are formed by chiral recognition. Dispersion of these porous microparticles in a range of size-excluded liquids, including oils and ionic liquids, forms stable POC-based Type III porous liquids. The flexible pairing between the solid POC particles and a carrier liquid allows the formation of a range of compositions, pore sizes, and other physicochemical properties to suit different applications and operating conditions. For example, it is shown that porous liquids with relatively low viscosities or high thermal stability can be produced. A 12.5 wt% Type III porous liquid comprising racemic POC microparticles and an ionic liquid, [BPy][NTf₂], shows a CO₂ working capacity (104.30 µmol g_L⁻¹) that is significantly higher than the neat ionic liquid (37.27 µmol g_L⁻¹) between 25 and 100 °C. This liquid is colloidally stable and can be recycled at least ten times without loss of CO₂ capacity.     

Generalized Synthetic Strategy for Amorphous Transition Metal Oxides-Based 2D Heterojunctions with Superb Photocatalytic Hydrogen and Oxygen Evolution

2D amorphous transition metal oxides (a-TMOs) heterojunctions that have the synergistic effects of interface (efficiently promoting the separation of electron−hole pairs) and amorphous nature (abundant defects and dangling bonds) have attracted substantial interest as compelling photocatalysts for solar energy conversion. Strategies to facilely construct a-TMOs-based 2D/2D heterojunctions is still a big challenge due to the difficulty of preparing individual amorphous counterparts. A generalized synthesis strategy based on supramolecular self-assembly for bottom–up growth of a-TMOs-based 2D heterojunctions is reported, by taking 2D/2D g-C₃N₄ (CN)/a-TMOs heterojunction as a proof-of-concept. This strategy primarily depends on controlling the cooperation of the growth of supramolecular precursor and the coordinated covalent bonds arising from the tendency of metal ions to attain the stable configuration of electrons, which is independent on the intrinsic character of individual metal ion, indicating it is universally applicable. As a demonstration, the structure, physical properties, and photocatalytic water-splitting performance of CN/a-ZnO heterojunction are systematically studied. The optimized 2D/2D CN/a-ZnO exhibits enhanced photocatalytic performance, the hydrogen (432.6 µmol h⁻¹ g⁻¹) and oxygen (532.4 µmol h⁻¹ g⁻¹) evolution rate are 15.5 and 12.2 times than bulk CN, respectively. This synthetic strategy is useful to construct 2D a-TMOs nanomaterials for applications in energy-related areas and beyond.     

Targeted Exfoliation and Reassembly of Polymeric Carbon Nitride for Efficient Photocatalysis

Switching the properties of photocatalytic materials targetedly and exerting these advantages fully in different photoredox reactions are crucial for the sufficient utilization of solar energy but still presents a significant challenge. This study presents a facile, green, and reversible exfoliation–reassembly strategy to switch the features of polymeric carbon nitride (CN) favorably for different photoredox reactions. The giant expansion effect of in situ‐generated H₂O molecules confined to the interlayer results in the mass production of ultrathin polymeric CN nanosheets, giving a high yield, i.e., up to 48%, of ultrathin nanosheets in a mild solution (pH ≈1.3). Interestingly, the exfoliation–reassembly process as well as the properties of CN are largely reversible via alternating the interlayer groups. Moreover, the exfoliated and reassembled CN achieve a superior photocatalytic activity for isopropanol degradation (acetone: 345 µmol h^?1; CO₂: 23 µmol h^?1) and H₂ evolution (1370 µmol h^?1), resulting in a high apparent quantum yield of 27% and 46%, respectively, at ≈420 nm.     

In Situ Photosynthesis of an MAPbI3/CoP Hybrid Heterojunction for Efficient Photocatalytic Hydrogen Evolution

Halide perovskite like methylammonium lead iodide perovskite (MAPbI₃) with its prominent optoelectronic properties has triggered substantial concerns in photocatalytic H₂ evolution. In this work, to attain preferable photocatalytic performance, a MAPbI₃/cobalt phosphide (CoP) hybrid heterojunction is constructed by a facile in situ photosynthesis approach. Systematic investigations reveal that the CoP nanoparticle can work as co‐catalyst to not only extract photogenerated electrons effectively from MAPbI₃ to improve the photoinduced charge separation, but also facilitate the interfacial catalytic reaction. As a result, the as‐achieved MAPbI₃/CoP hybrid displays a superior H₂ evolution rate of 785.9 µmol h^?1 g^?1 in hydroiodic acid solution within 3 h, which is ≈8.0 times higher than that of pristine MAPbI₃. Furthermore, the H₂ evolution rate of MAPbI₃/CoP hybrid can reach 2087.5 µmol h^?1 g^?1 when the photocatalytic reaction time reaches 27 h. This study employs a facile in situ photosynthesis strategy to deposit the metal phosphide co‐catalyst on halide perovskite nanocrystals to conduct photocatalytic H₂ evolution reaction, which may stimulate the intensive investigation of perovskite/co‐catalyst hybrid systems for future photocatalytic applications.     

Heteroatom- and Bonded Z-Scheme Channels-Modulated Ultrafast Carrier Dynamics and Exciton Dissociation in Covalent Triazine Frameworks for Efficient Photocatalytic Hydrogen Evolution

Covalent triazine frameworks (CTF) offer a tunable platform for photocatalytic H₂ generation due to their diverse structures, low costs, and precisely tunable electronic structures. However, high exciton binding energy and short lifetimes of photogenerated carriers restrict their application in photocatalytic hydrogen evolution. Herein, a novel phosphorus-incorporated CTF is introduced to construct a chemically bonded PCTF/WO₃ (PCTFW) heterostructure with a precise interface electron transfer channel. The phosphorus incorporation is found to dominantly reduce the exciton binding energy and promote the dissociation of singlet and triplet excitons into free charge carriers due to the regulation of electronic structures. High-quality interfacial W N bonds improve the interfacial transfer of photogenerated electrons, thus prolonging the lifetime of photogenerated electrons. Femtosecond transient absorption spectroscopy characterizations and DFT calculations further confirm both phosphorus incorporation and Z-scheme heterojunctions can synergistically boost the in-built electric field and accelerate the migration and separation of photogenerated electrons. The optimized photocatalytic H₂-evolution rate of resultant PCTFW is 134.84 µmol h⁻¹ (67.42 mmol h⁻¹g⁻¹), with an apparent quantum efficiency of 37.63% at 420 nm, surpassing many reported CTF-based photocatalysts so far. This work highlights the significance of atom-level interfacial exciton dissociation, and charge transfer and separation in improving photocatalysis.     

Surface Energy Mediated Sulfur Vacancy of ZnIn2S4 Atomic Layers for Photocatalytic H2O2 Production

Constructing rich defect active site structure for material design is still a great challenge. Herein, a simple surface engineering strategy is demonstrated to construct one-unit-cell ZnIn₂S₄ atomic layers with the modulated surface energy of S vacancy. Rich surface energy can regulate and control the rich S vacancy, which ensures rich active sites, higher charge density and effective carrier transport. As a result, the ZnIn₂S₄ atomic layers with rich surface energy affords an obvious enhancement in H₂O₂ productive rate of 1592.04 µmol g⁻¹ h⁻¹, roughly 14.58 times superior to that with poor surface energy. Moreover, the in situ infrared diffuse reflection spectrum indicates that S vacancy as the oxygen reduction reaction active site is responsible for the critical intermediate *O₂⁻ and *OOH, corresponding to two-electron oxygen reduction reaction. This study provides a valuable insight and guidance for constructing controllably defects to achieve highly efficient H₂O₂ production.     

Tailoring Antibonding-Orbital Occupancy State of Selenium in Se-Enriched ReSe2+x Cocatalyst for Exceptional H2 Evolution of TiO2 Photocatalyst

Electron density regulation of active sites can realize an optimal hydrogen-binding strength, whereas the underlying regulation mechanism is still indistinct. Herein, a new concept of antibonding-orbital occupancy state is first proposed to unveil the fundamental influence mechanism of electron density on the Se H_ads bond strength for achieving first-rank adsorption energy toward atomic hydrogen by constructing Se-enriched surrounding to form electron-deficient Se^(2-δ)- active sites in ReSe_2+x nanodots. To this end, the Se-rich ReSe_2+x nanodots (0.3–1 nm) can be dexterously fabricated onto the TiO₂ to prepare Se-rich ReSe_2+x/TiO₂ by an ingenious one-step photosynthesis route. In a surprise, a large number of visual H₂ bubbles are continuously produced on the resultant ReSe_2+x/TiO₂(0.7 wt.%) with an ultrahigh rate of 12 490.4 µmol h⁻¹ g⁻¹ and an apparent quantum efficiency of 60.0%, which is 5.0 times higher than that of traditional ReSe₂/TiO₂, even comparable with benchmark Pt/TiO₂(0.7 wt.%). In situ/ex situ XPS characterizations coupled with density functional theory (DFT) calculations corroborate that a Se-enriched environment can induce the formation of electron-deficient Se^(2-δ)− and then reduce its antibonding-orbital occupancy state, thus increasing the stability of H 1s-p antibonding and accordingly reinforcing the Se H_ads bonds. This holistic study identifies the dominant role of antibonding-orbital occupancy states in the optimization of hydrogen-binding energy.     

Atomically Dispersed Unsaturated Cu-N3 Sites on High-Curvature Hierarchically Porous Carbon Nanotube for Synergetic Enhanced Nitrate Electroreduction to Ammonia

Cu-based single-atom catalysts (SACs) are regarded as promising candidates for electrocatalytic reduction of nitrate to ammonia (NO₃RR) owing to the appropriate intrinsic activity and the merits of SACs. However, most reported Cu SACs are based on 4N saturated coordination and supported on planer carbon substrate, and their performances are unsatisfactory. Herein, low-coordinated Cu-N₃ SACs are designed and constructed on high-curvature hierarchically porous N-doped carbon nanotube (NCNT) via a stepwise polymerization–surface modification–electrostatic adsorption–carbonization strategy. The Cu-N₃ SACs/NCNT exhibits outstanding NO₃RR performance with maximal Faradaic efficiency of 89.64% and NH₃ yield rate of up to 30.09 mg mg_cat⁻¹ h⁻¹ (70.8 mol g_Cu⁻¹ h⁻¹), superior to most reported SACs and Cu-based catalysts. The results integrated from potassium thiocyanide poisoning experiments, online differential electrochemical mass spectrometry, in situ Fourier transform infrared spectroscopy, and density functional theory calculations demonstrate: 1) unsaturated Cu is active site; 2) Cu-N₃ SACs/NCNT possesses NO*-HNO*-H₂NO*-H₂NOH* pathway; 3) low-coordinated Cu-N₃ sites and high-curvature carbon support synergetic promote reaction dynamics and reduce rate-determining step barrier. This study inspires a synergetic enhancement catalysis strategy of creating unsaturated coordination environment and regulating support structure.     

Pre-Adsorbed H-Assisted N2 Activation on Single-Atom Cadmium-O5 Decorated In2O3 for Efficient NH3 Electrosynthesis

The electrocatalytic nitrogen reduction reaction (NRR) provides a promising avenue for sustainable and decentralized green ammonia (NH₃) synthesis. To promote the NRR, the design and synthesis of efficient electrocatalysts with an elucidated reaction mechanism is critically important. Here, surface hydrogenation-facilitated NRR is demonstrated to yield NH₃ at low overpotentials on oxygen-deficient In₂O₃ plates decorated with single atom CdO₅ that have a weak N₂-binding capability. Adsorbed ^*H is calculated to be first produced via the Volmer reaction (H₂O + e⁻ → ^*H + OH⁻) and then reacts with dissolved N₂ to generate ^*N₂H₂, which is likely the rate determining step (RDS) of the whole process. Cd atoms and oxygen vacancies in In₂O₃ jointly enhance the activation of N₂ and accelerate the RDS, boosting the NRR. An NH₃ production rate of as high as 57.5 µg h⁻¹ mg_cat⁻¹ is attained at a mild potential, which is retained to a large extent even after 44 h of continuous polarization.     

Proton Turnover Dominated Cascade Route for CO2 Photoreduction

Photoreduction carbon dioxide (CO₂) and water (H₂O) into valuable chemicals is a huge potential to mitigate immoderate CO₂ emissions and energy crisis. To date, tremendous attention is concentrated on the improvement of independent CO₂ reduction or H₂O oxidation behaviors. However, the simultaneous control of efficient electron and hole utilization is still a huge challenge due to the complex cascade redox reactions. Here, a proton turnover exists in the whole CO₂ photoreduction process is discovered, which is defined as the pivot to concatenate the hole and electron behaviors. As a demonstration of the concept, the efficient activated hydrogen (*H) production centers of copper (Cu) and rapid hydrogenation centers of nickel (Ni) are coupled by an alloying strategy, and the proton turnover behaviors could be directly determined by adjustment of the molar ratios of Cu_xNi_y. Moreover, Cu₃Ni₁–TiO₂ exhibits the highest electron selectivity of 93.7% for methane (CH₄) production with a rate of 175.9 µmol g⁻¹ h⁻¹, while Cu₁Ni₅–TiO₂ reaches up to the highest carbon monoxide (CO) electron selectivity and generation rate at 84.4% and 164.6 µmol g⁻¹ h⁻¹, respectively. Consequently, the experimental and theoretical analysis all clarify the predominate proton turnover effect during the overall CO₂ photoreduction process, which directly determines the categories and generated efficiency of C-based products by regulating variable reaction pathways. Therefore, the revelation of the proton turnover pivot could broaden the new sights by bidirectional optimization of dynamics during the overall CO₂ photoreduction system, which favors the efficient, selective, and stable photocatalytic CO₂ reduction with H₂O.     

Coupling Piezocatalysis and Photocatalysis in Bi4NbO8X (X = Cl,Br) Polar Single Crystals

Reactive oxygen species (ROS) as green oxidants are of great importance for environmental and biological applications. Photocatalysis is one of the major routes for ROS evolution, which is seriously restricted by rapid charge recombination. Herein, piezocatalysis and photocatalysis (i.e., piezo–photocatalysis) are coupled to efficiently produce superoxide radicals (?O₂^?), hydrogen peroxide (H₂O₂), and hydroxyl radicals (?OH) via oxygen reduction reaction (ORR), by using Bi₄NbO₈X (X = Cl, Br) single crystalline nanoplates. Significantly, the piezo‐photocatalytic process leads to the highest ORR performance of the Bi₄NbO₈Br nanoplates, exhibiting ?O₂^?, H₂O₂, and ?OH evolution rates of 98.7, 792, and 33.2 µmol g^?1 h^?1, respectively. The formation of a polarized electric field and band bending allows directional separation of charge carriers, promoting the catalytic activity. Furthermore, the reductive active sites are found enriched on all the facets in the piezo–photocatalytic process, also contributing to the ORR. By piezo–photodeposition of Pt to artificially plant reductive reactive sites, the Bi₄NbO₈Br plates demonstrate largely enhanced photocatalytic H₂ production activity with a rate of 203.7 µmol g^?1 h^?1. The present work advances piezo–photocatalysis as a new route for ROS generation, but also discloses the potential of piezo–photocatalytic active sites enriching for H₂ evolution.     

Atomistic Structural Engineering of Conjugated Microporous Polymers Promotes Photocatalytic Biomass Valorization

Polymer photocatalysts have great promise for solar fuel production due to their flexible structural and functional designability. However, their photocatalytic efficiencies are still unsatisfactory, limited by their intrinsically large exciton binding energy and fast charge recombination. Herein, the atomistic structural engineering of donor–acceptor (D−A) polymer photocatalysts for enhanced charge separation and photocatalytic hydrogen production is proposed. By changing the electron affinity of the acceptor units, the electron delocalization and exciton binding energy of the polymeric networks can be readily tuned, resulting in enhanced charge separation efficiency and photocatalytic activity. The optimal sample shows the highest H₂ production rate of 3207 µmol g⁻¹ h⁻¹ in the presence of ascorbic acid as the sacrificial agent. Moreover, the photocatalytic H₂ production can be coupled with almost stoichiometrical conversion of 5-hydroxymethyl furfural to 2,5-diformylfuran.     

Triple Interface Optimization of Ru-based Electrocatalyst with Enhanced Activity and Stability for Hydrogen Evolution Reaction

A challenging task is to promote Ru atom economy and simultaneously alleviate Ru dissolution during the hydrogen evolution reaction (HER) process. Herein, Ru nanograins (≈1.7 nm in size) uniformly grown on 1T-MoS₂ lace-decorated Ti₃C₂T_x MXene sheets (Ru@1T-MoS₂-MXene) are successfully synthesized with three types of interfaces (Ru/MoS₂, Ru/MXene, and MoS₂/MXene). It gives high mass activity of 0.79 mA µg_Ru⁻¹ at an overpotential of 100 mV, which is ≈36 times that of Ru NPs. It also has a much smaller Ru dissolution rate (9 ng h⁻¹), accounting for 22% of the rate for Ru NPs. Electrochemical tests, scanning electrochemical microscopy measurements combined with DFT calculations disclose the role of triple interface optimization in improved activity and stability. First, 2D MoS₂ and MXene can well disperse and stabilize Ru grains, giving larger electrochemical active area. Then, Ru/MoS₂ interfaces weakening H^* adsorption energy and Ru/MXene interfaces enhancing electrical conductivity, can efficiently improve the activity. Next, MoS₂/MXene interfaces can protect MXene sheet edges from oxidation and keep 1T-MoS₂ phase stability during the long-term catalytic process. Meanwhile, Ru@1T-MoS₂-MXene also displays superior activity and stability in neutral and alkaline media. This work provides a multiple-interface optimization route to develop high-efficiency and durable pH-universal Ru-based HER electrocatalysts.     

Reactive Oxygenated Species Generated on Iodide-Doped BiVO4/BaTiO3 Heterostructures with Ag/Cu Nanoparticles by Coupled Piezophototronic Effect and Plasmonic Excitation

An effective generation of reactive oxygen species (ROS) is of interest from the perspective of environmental technology and industrial chemistry, and here piezocatalysis and photocatalysis using heterostructures based on iodide-doped BiVO₄/BaTiO₃ with photodeposited Ag or Cu nanoparticles (BiVO₄:I/BTO-Ag or BiVO₄:I/BTO-Cu) is studied. The generation rates of •OH and •O₂⁻ radicals over BiVO₄:I/BTO-Ag during piezophotocatalysis are 371 and 292 µmol g⁻¹ h⁻¹, respectively, and significantly higher than those of sole piezocatalysis and photocatalysis. These rates are among the highest reported for the production of free radicals with the piezophototronic effect. Among the catalysts, BiVO₄:I/BTO shows the highest reactivity for the production of H₂O₂ in piezocatalysis (with a concentration of 468 µm after 100 min of irradiation, and still constantly increasing). On BiVO₄:I/BTO-Ag and BiVO₄:I/BTO-Cu, it seems that redundant electrons and holes had reacted effectively with the generated H₂O₂ and in turn had reduced their activities; however, the amounts of H₂O₂ that are formed on BiVO₄:I/BTO-Ag or BiVO₄:I/BTO-Cu under piezophotocatalysis are superior to those of individual piezocatalysis and photocatalysis. A piezophototronic coupling via an ultrasound-mediated and piezoelectric-based polarization field and photoexcitation accounting for the enhanced photocatalytic activity of the iodine-doped heterostructures with plasmonically sized Ag or Cu nanoparticles is suggested.     

Phosphorus Optimized Metastable Hexagonal-Close-Packed Phase Nickel for Efficient Hydrogen Peroxide Production in Neutral Media

Direct synthesis of hydrogen peroxide (H₂O₂) through electrochemical oxygen reduction has gained close attention yet remains a great challenge due to the slow kinetics. Herein, combining with the virtues of the native high energy state and fascinating surface environment of metastable materials and doping strategy, an efficient phosphorus-optimized metastable hexagonal-close-packed phase nickel catalyst (P-hcp Ni), belonging to the space group (P63/mmc, 194), with P doping is demonstrated. Significantly, it achieves high selectivity of 97% and a high intrinsic turnover frequency of 2.34 s⁻¹, much better than those of the stable face-centered-cubic Ni catalyst. It also displays high stability with remaining in the metastable phase after the stability test. More importantly, P-hcp Ni also achieves a productivity of 4917.2 mmol g_Ni⁻¹ h⁻¹ and an accumulated concentration of (H₂O₂) of 2.38 mol L⁻¹ after 130 h stability test in pure water with a solid electrolyte. Further investigation reveals that the P doping not only greatly enhances the stability of metastable phase, but also weakens the *OOH adsorption on the active site, promoting the high production of H₂O₂ in the neutral media.