Highest Apparent Quantum Yield Research Articles

Mixed Crystalline Covalent Heptazine Frameworks with Built‐in Heterojunction Structures towards Efficient Photocatalytic Formic Acid Dehydrogenation

Covalent heptazine frameworks (CHFs) are widely utilized in the recent years as potential photocatalysts. However, their limited conjugated structures, low crystallinity and small surface areas have limited the practical photocatalysis performance. Along this line, we report herein the synthesis of a kind of mixed crystalline CHF (m‐CHF‐1) with built‐in heterojunction structure, which can efficiently catalyze the formic acid dehydrogenation by visible light driven photocatalysis. The m‐CHF‐1 is synthesized from 2,5,8‐triamino‐heptazine and dicyanobenzene (DCB) in the molten salts, in which DCB plays as organic molten co‐solvent to promote the rapid and ordered polymerization of 2,5,8‐triamino‐heptazine. The m‐CHF‐1 is formed by embedding phenyl‐linked heptazine (CHF‐Ph) units in the poly(heptazine imide) (PHI) network similar to doping. The CHF‐Ph combined with PHI form an effective type II heterojunction structure, which promote the directional transfer of charge carriers. And the integration of CHF‐Ph makes m‐CHF‐1 have smaller exciton binding energy than pure PHI, the charge carriers are more easily dissociated to form free electrons, resulting in higher utilization efficiency of the carriers. The largest hydrogen evolution rate reaches a value of 42.86 mmol h‐1 g‐1 with a high apparent quantum yield of 24.6% at 420 nm, which surpasses the majority of other organic photocatalysts.

Mixed Crystalline Covalent Heptazine Frameworks with Built-in Heterojunction Structures towards Efficient Photocatalytic Formic Acid Dehydrogenation.

Covalent heptazine frameworks (CHFs) are widely utilized in the recent years as potential photocatalysts. However, their limited conjugated structures, low crystallinity and small surface areas have limited the practical photocatalysis performance. Along this line, we report herein the synthesis of a kind of mixed crystalline CHF (m-CHF-1) with built-in heterojunction structure, which can efficiently catalyze the formic acid dehydrogenation by visible light driven photocatalysis. The m-CHF-1 is synthesized from 2,5,8-triamino-heptazine and dicyanobenzene (DCB) in the molten salts, in which DCB plays as organic molten co-solvent to promote the rapid and ordered polymerization of 2,5,8-triamino-heptazine. The m-CHF-1 is formed by embedding phenyl-linked heptazine (CHF-Ph) units in the poly(heptazine imide) (PHI) network similar to doping. The CHF-Ph combined with PHI form an effective type II heterojunction structure, which promote the directional transfer of charge carriers. And the integration of CHF-Ph makes m-CHF-1 have smaller exciton binding energy than pure PHI, the charge carriers are more easily dissociated to form free electrons, resulting in higher utilization efficiency of the carriers. The largest hydrogen evolution rate reaches a value of 42.86 mmol h-1 g-1 with a high apparent quantum yield of 24.6% at 420 nm, which surpasses the majority of other organic photocatalysts.

Boosted Charge Transfer for Highly Efficient Photosynthesis of H2O2 over Z‐Scheme I−/K+ Co‐Doped g‐C3N4/Metal–Organic‐Frameworks in Pure Water under Visible Light

AbstractPhotocatalytic oxygen reduction reaction (ORR) is an environmentally friendly and cost‐effective approach for H2O2 synthesis. However, the current photosynthesis system suffers from sluggish kinetics, rapid recombination of photoexcited charge carriers, and weak redox potentials, resulting in unsatisfactory solar‐to‐chemical conversion efficiency. Herein, a Z‐scheme heterojunction (UiO/IKCN) is constructed through coupling I−/K+ co‐doped g‐C3N4 (IKCN) with NH2‐UiO‐66, a typical metal‐organic framework material. Under visible light irradiation, the optimal UiO/IKCN exhibits exceptional H2O2 production rates in pure water (13.3 mM g−1 h−1) and in isopropanol solution (72.6 mM g−1 h−1), that is 48.4 times higher than pristine CN in isopropanol (1.5 mM g−1 h−1). A high apparent quantum yield of 10.28% at 420 nm is achieved by UiO/IKCN, surpassing most previously reported values. The dominating role of two‐electron ORR in H2O2 photosynthesis is elucidated in detail. The significantly enhanced photocatalytic activity can be attributed to the facilitated charge separation and Z‐scheme charge transfer, which are unambiguously verified by stable‐state surface photovoltage, transient photoluminescence, femtosecond transient absorption spectroscopy, in‐situ irradiated X‐ray photoelectron spectroscopy, and density functional theory calculations. This study represents the first exploration of H2O2 production using NH2‐UiO‐66 and provides insights into the rational design of Z‐scheme heterojunction for highly efficient photosynthesis.

Resorcinol‐Phthalaldehyde Resins for Photosynthesis of Hydrogen Peroxide: Modulation of Electronic Structure and Integration of Dual Channel Pathway

AbstractModulating of electronic structure of photocatalyst and integration of dual channel pathway are promising strategy for efficient photosynthesis of hydrogen peroxide (H2O2) from pure water without sacrificial agent and oxygen exposure. In this work, nontoxic aromatic dialdehyde is used to replace the commonly used toxic formaldehyde to form resorcinol‐phthalaldehyde resins through a hydrothermal method. The introducing of aromatic ring as π spacer increases the separation distance of electrons and holes to avoid their recombination. H2O2 can be produced via integrated oxygen reduction reaction (ORR) and water oxidation reaction (WOR) due to the suitable energy band positions and spatially separated reaction sites. Resorcinol‐p‐phthalaldehyde (RP) resin exhibits a promising H2O2 yield of 3351 µmol g−1 h−1 with high apparent quantum yield (AQY) of 14.9% at 420 nm and solar‐to‐chemical conversion (SCC) efficiency of 1.54%. This work provides a simple strategy to modulate the charge separation efficiency and redox reaction pathway on photocatalyst at molecular level design.

Multi-vacancy synergistic effect in a NiSe0.4S1.6/ZnO heterostructure for promoting photocatalytic hydrogen production

Defect engineering is one of the methods to improve catalytic activity of photocatalysts, but there are few reports on multi-vacancy systems. In this paper, S doping NiSe2 (NiSe0.4S1.6, NSS) was synthesized and further the NSS/xZnO heterostructures containing Ni, Se and O vacancies were constructed. The hydrogen and active oxygen ions are in situ generated at oxygen vacancy (VO) in ZnO, which greatly reduce the recombination of photocarriers, and the generated active oxygen ions and sacrificial agent anions (S2−, SO32−) involve in the regeneration of oxygen vacancy, which may be one of the reasons for the high activity and stability of the composite catalysts. The polarization electric field is formed by regulating the selenium and nickel double vacancy (VSe, VNi) generated by doping NiSe2 with S, which further improves the charge separation leading to the promotion of photocatalytic hydrogen production. The synergistic effect of the three types of vacancies and the redox properties of the composite catalyst lead to a high H2 production rate of 17.04 mmol·g−1·h−1, 54 and 76 times higher than NSS and ZnO, and a high apparent quantum yield of 15.30 % at 400 nm. The hydrogen production mechanism was explored by EPR, Mott-Schottky, VB-XPS, in suit XPS, DFT, etc. This work proves that the combination of transition metal oxides with rich oxygen defects and metal chalcogenides with metal and chalcogen di-vacancies containing local polarized electric fields is an effective strategy to design high active photocatalyts for water splitting.

Coupling amorphous WO3 with WP as a cocatalyst for efficient dye-sensitizated photocatalytic hydrogen evolution

Tungsten phosphide (WP) as an excellent hydrogen evolution reactions (HER) catalyst has attracted widespread attention, but its HER activity is low in alkaline media due to high water dissociation barrier. Herein, noble-metal-free cocatalyst WP/WO3 composite was synthesized by adjusting the P/W molar ratio in the raw material using a simple solid phosphidation reaction. The structure, morphology, composition, and optoelectronic properties of the as-synthesized samples were characterized by XRD, SEM, TEM, XPS, UV–vis DRS, PL techniques, and electrochemical methods. Under visible light irradiation (λ ≥ 420 nm), the photocatalytic HER activities of the as-prepared samples using Eosin-Y (EY) dye as a sensitizer and trimethylamine (TMA) as an electron donor were investigated. The result shows that WP/WO3 composite as a cocatalyst exhibits excellent photocatalytic HER activity and good stability. The highest apparent quantum yield (AQY) reaches 32.8 %. The presence of amorphous WO3 in crystalline WP can improve the separation efficiency of photogenerated electrons and holes, reduce HER overpotential, and promote the dissociation of H2O in alkaline media. Therefore, the photocatalytic HER activity of WP/WO3 composite is higher than that of single crystalline WP.

Reduced Graphene Oxide–SnSe Nanocomposite Photocatalyst with High Apparent Quantum Yield for the Photodegradation of Norfloxacin

Reduced Graphene Oxide–SnSe Nanocomposite Photocatalyst with High Apparent Quantum Yield for the Photodegradation of Norfloxacin

1D Covalent Organic Frameworks Triggering Highly Efficient Photosynthesis of H2 O2 via Controllable Modular Design.

The topological diversity of covalent organic frameworks (COFs) enables considerable space for exploring their structure-performance relationships. In this study, we report a sequence of novel 1D COFs (EO, ES, and ESe-COF) with typical 4-c sql topology that can be interconnected with VIA group elements (O, S, and Se) via a modular design strategy. It is found that the electronic structures, charge delivery property, light harvesting ability, and hydrophilicity of these 1D COFs can be profoundly influenced by the bridge-linked atom ordinal. Finally, EO-COF, possessing the highest quantity of active sites, the longest lifetime of the active electron, the strongest interaction with O2 , and the lowest energy barrier of O2 reduction, exhibits exceptional photocatalytic O2 -to-H2 O2 activity under visible light, with a production rate of 2675 μmol g-1 h-1 and a high apparent quantum yield of 6.57 % at 450 nm. This is the first systematic report on 1D COFs for H2 O2 photosynthesis, which enriches the topological database in reticular chemistry and promotes the exploration of structure-catalysis correlation.

1D Covalent Organic Frameworks Triggering Highly Efficient Photosynthesis of H2O2 via Controllable Modular Design

AbstractThe topological diversity of covalent organic frameworks (COFs) enables considerable space for exploring their structure‐performance relationships. In this study, we report a sequence of novel 1D COFs (EO, ES, and ESe‐COF) with typical 4‐c sql topology that can be interconnected with VIA group elements (O, S, and Se) via a modular design strategy. It is found that the electronic structures, charge delivery property, light harvesting ability, and hydrophilicity of these 1D COFs can be profoundly influenced by the bridge‐linked atom ordinal. Finally, EO‐COF, possessing the highest quantity of active sites, the longest lifetime of the active electron, the strongest interaction with O2, and the lowest energy barrier of O2 reduction, exhibits exceptional photocatalytic O2‐to‐H2O2 activity under visible light, with a production rate of 2675 μmol g−1 h−1 and a high apparent quantum yield of 6.57 % at 450 nm. This is the first systematic report on 1D COFs for H2O2 photosynthesis, which enriches the topological database in reticular chemistry and promotes the exploration of structure‐catalysis correlation.

Anisotropic Charge Migration on Perovskite Oxysulfide for Boosting Photocatalytic Overall Water Splitting.

The synthesis of photocatalysts with both broad light absorption and efficient charge separation is significant for a high solar energy conversion, which still remains to be a challenge. Herein, a narrow-bandgap Y2Ti2O5S2 (YTOS) oxysulfide nanosheet coexposed with defined {101} and {001} facets synthesized by a flux-assisted solid-state reaction was revealed to display the character of an anisotropic charge migration. The selective photodeposition of cocatalysts demonstrated that the {101} and {001} surfaces of YTOS nanosheets were the reduction and oxidation regions during photocatalysis, respectively. Density functional theory (DFT) calculations indicated a band energy level difference between the {101} and {001} facets of YTOS, which contributes to the anisotropic charge migration between them. The exposed Ti atoms on the {101} surface and S atoms on the {001} surface were identified, respectively, as reducing and oxidizing centers of YTOS nanosheets. This anisotropic charge migration generated a built-in electric field between these two facets, quantified by spatially resolved surface photovoltage microscopy, the intensity of which was found to be highly correlated with photocatalytic H2 production activity of YTOS, especially exhibiting a high apparent quantum yield of 18.2% (420 nm) after on-site modification of a Pt@Au cocatalyst assisted by Na2S-Na2SO3 hole scavengers. In conjunction with an oxygen-production photocatalyst and a [Co(bpy)3]2+/3+ redox shuttle, the YTOS nanosheets achieved a solar-to-hydrogen conversion efficiency of 0.15% via a Z-scheme overall water splitting. Our work is the first to confirm anisotropic charge migration in a perovskite oxysulfide photocatalyst, which is crucial for enhancing charge separation and surface catalytic efficiency in this material.

Cationic surface polarization centers on ionic carbon nitride for efficient solar-driven H2O2 production and pollutant abatement

Solar-driven H2O2 production and emerging organic pollutants (EOPs) elimination are of great significance from the perspective of environmental sustainability. The efficiency of the photocatalytic reaction system is the key challenge to be addressed. In this work, the strategy of constructing surface ionic local polarization centers to enhance the exciton dissociation of the polymeric photocatalytic is demonstrated. Selected bipyridinium cation (TMAP) is complexed on a K+-incorporated carbon nitride (CNK) framework, and the combination of local polarization centers both on the surface (bipyridinium cation) and bulk (K+ cation) contributes to a superior photocatalytic H2O2 production performance, affording a remarkable H2O2 generation rate of 46.8 µmol h−1 mg−1 and a high apparent quantum yield (AQY) value of 77.5% under irradiation of 405 nm photons. As substantiated experimentally by steady state/transient spectroscopy techniques, the surface local polarization centers increase the population of the long-lived trapped electrons, and thereby promote the interfacial charge transfer process for chemical conversion reaction. The strategy is potentially applicable to the design of a wide range of efficient solar-to-chemical conversion systems.

An S-scheme heterointerface-engineered high-performance ternary NiAl-LDH@TiO2/Ti3C2 MXene photocatalytic system for solar-powered CO2 reduction to produce energy-rich fuels

While there is much potential for photocatalytic CO2 reduction, poor light absorption and high recombination rates of photogenerated charges limit its effectiveness. To address these challenges, we systematically developed a heterointerface-engineered ternary hybrid photocatalyst comprising NiAl-layered double hydroxide (LDH), titanium dioxide (TiO2), and titanium carbide (Ti3C2) MXene via an in situ growth approach. As a result of the unique combination of these three components, the synthesized ternary NiAl-LDH@TiO2/Ti3C2 photocatalyst demonstrated broad light absorption spanning across the ultraviolet, visible, and near-infrared regions, as well as elevated CO2 adsorption capacity. In situ-irradiated X-ray photoelectron spectroscopy and electron paramagnetic resonance analyses provided compelling evidence for an unconventional S-scheme charge transfer mechanism in the ternary system that effectively separates the charges and suppresses recombination, allowing NiAl-LDH to maintain its strong reducing capacity and TiO2 to maintain its robust oxidizing capacity. Utilizing the complementary and synergistic properties of these three components (NiAl-LDH, TiO2, and Ti3C2), an optimized ternary NiAl-LDH@TiO2/Ti3C2 photocatalyst with 30 wt% Ti3C2 exhibited extraordinary solar-driven CO2 reduction performance with a remarkable 99 % CO selectivity against competitive H2 production and a high apparent quantum yield of 0.81 at 365 nm. Additionally, the ternary photocatalyst exhibited excellent stability, maintaining its performance capacity over multiple CO2 reduction cycles. This work provides a fresh perspective on designing and creating efficient ternary S-scheme photocatalytic systems for solar-driven CO2 reduction and highlights the potential for energy-rich fuel production.

Bandgap-energy-adjustable noble-metal-free MoS2-ZnxCd1−xS for highly efficient H2 production under visible-light

BackgroundRecognized for its high calorific value, clean and non-polluting properties, hydrogen is considered to be one of the most attractive solutions to the impending energy crisis. Photocatalytic water splitting has been widely investigated for its promise to produce hydrogen in a sustainable, environmentally friendly and low-cost approach. In pursuit of high photocatalytic efficiency, multiple strategies haven been explored such as doping, co-catalyst modification and heterojunction construction realizing promising improvements. MethodsWe synthesized CdS doped with Zn ions and modified with MoS2 as co-catalyst to form ZnxCd1−xS solid solution and MoS2-Zn0.25Cd0.75S heterojunction using a simple one-step hydrothermal method. The synthesized catalyst was used water splitting under visible light irradiation. The structural and morphological characteristics of these materials, along with their photocatalytic mechanisms, were investigated using multiple techniques such as SEM, TEM, XPS, PL, etc. FindingsThe photocatalyst consisting of 0.9 wt.% MoS2-Zn0.25Cd0.75S achieved a production rate of 6276 μmol h−1 g−1, which is 17.4 times higher than that of pure CdS and 1.6 times higher than that of Zn0.25Cd0.75S. The composite also demonstrated a high apparent quantum yield of 11.1 % at 420 nm. The mechanism of the water splitting process, revealed through various techniques, introduces novel pathways for crafting high-efficiency photocatalysts with an internal electron-hole separation heterostructure.

Enhancing photocatalytic hydrogen production of carbon nitride: Dominant advantage of crystallinity over mass transfer

Mass transfer enhancement and crystallinity engineering are two prevailing technologies for photocatalyst modification. However, their relative effectiveness in enhancing photocatalytic activity remains unclear due to the lack of rational probing catalysts. In this study, we synthesized two distinct carbon nitride (C3N4) catalysts: one with a high specific surface area (CN-HA) and the other with improved crystallinity (CN-HC). These catalysts served as probes to compare their respective impacts on photocatalytic activities. Comprehensive characterization techniques and density functional theory (DFT) calculation results unveiled that crystallinity played a dominant role in light absorption and charge dynamics, while surface area primarily influenced mass transfer in photocatalysis. Importantly, our findings revealed that crystallinity engineering of photocatalyst achieved a greater impact on photocatalytic hydrogen evolution than that from mass transfer enhancement. Consequently, CN-HC demonstrated a remarkable improvement in photocatalytic performance for hydrogen evolution (6465.4 μmol h−1 g−1), surpassing both C3N4 and CN-HA by 19.4- and 2.4-fold, respectively, accompanied by a high apparent quantum yield of 23.8 % at 420 nm. This study not only unveils the dominant factor influencing the activity of photocatalysts but also provides a modified approach for robust solar fuel production, shedding light on the path toward efficient and sustainable energy conversion.

A feasible preparation of leaf like 3D dendrite MnxCd1-xS with photocatalytic hydrogen evolution

It is well known that both the size and morphology of semiconductor photocatalysts impact their performance. No template synthesis is the future trend. In this study, a series of MnxCd1-xS photocatalysts with a leaf-shaped three-dimensional (3D) dendrite structure was prepared by hydrothermal method without the addition of template agent and surfactant. The hydrogen production rate of leaf-like dendrite MnxCd1-xS was tested under visible light irradiation with Pt as co-catalyst. The highest hydrogen production rate was 1360 μmol g−1 h−1 and the highest apparent quantum yield (AQY) at 450 nm was 3.64%. In addition, the leaf-shaped MnxCd1-xS has good cycling stability and can be used repeatedly. Finally, a reasonable reaction mechanism was proposed based on the experimental consequences. This work provides a feasible strategy for the construction of MnxCd1-xS solid solutions with new morphologies.

Position-selected cocatalyst modification on a Z-scheme Cd0.5Zn0.5S/NiTiO3 photocatalyst for boosted H2 evolution

Photocatalytic water splitting by semiconductors is a promising technology to produce clean H2 fuel, but the efficiency is restrained seriously by the high overpotential of the H2-evolution reaction together with the high recombination rate of photoinduced charges. To enhance H2 production, it is highly desirable yet challenging to explore an efficient reductive cocatalyst and place it precisely on the right sites of the photocatalyst surface to work the proton reduction reaction exclusively. Herein, the metalloid NixP cocatalyst is exactly positioned on the Z-scheme Cd0.5Zn0.5S/NiTiO3 (CZS/NTO) heterostructure through a facile photodeposition strategy, which renders the cocatalyst form solely at the electron-collecting locations. It is revealed that the directional transfer of photoexcited electrons from Cd0.5Zn0.5S to NixP suppresses the quenching of charge carriers. Under visible light, the CZS/NTO hybrid loaded with the NixP cocatalyst exhibits an optimal H2 yield rate of 1103 μmol h−1 (i.e., 27.57 mmol h−1 g−1), which is about twofold of pristine CZS/NTO and comparable to the counterpart deposited with the Pt cocatalyst. Besides, the high apparent quantum yield (AQY) of 56% is reached at 400 nm. Further, the mechanisms of the cocatalyst formation and the H2 generation reaction are discussed in detail.

Atomically isolated copper on titanium dioxide for ammonia photosynthesis via nitrate reduction with unprecedently high apparent quantum yield

Photocatalytic nitrate (NO3) reduction to NH3 (PcNRA) is a sustainable alternative that is considered advantageous over N2 fixation, which suffers from the high dissociation energy and sluggish activation of inactive N2. Although PcNRA has recently been shown to achieve excellent selectivity, its sluggish kinetics restrict the NH3 production efficiency. Herein, we present a single-atom Cu-incorporated TiO2 nanosheet (Cu-TNS) photocatalyst for efficient and selective PcNRA. Single Cu atoms displacing Ti sites accumulate photogenerated electrons, ensuring efficient charge separation and surface NO3 reduction. Moreover, introducing Cu atoms into the TiO2 matrix induces spontaneous defect formation, resulting in oxygen vacancies and lattice strain that promote NO3 adsorption and activation. The simultaneous presence of single Cu atoms and structural defects in Cu-TNS synergistically stimulates PcNRA, leading to a 62-fold enhancement over pristine TiO2 in NH3 production with 97.6% selectivity and an unprecedently high apparent quantum yield of 11.7% at 330 nm under optimized conditions.

Conjugated porous polymers regulated by thiophene and polycyclic aromatic hydrocarbons for photocatalytic water splitting toward hydrogen production

Rational design of organic semiconductors with wide visible light absorption and quick charge separation is of great significance for photocatalytic hydrogen production form water. In this work, the chemical structure of a linear conjugated polymer composed of ethynyl-linked benzene (B) and 2,1,3-benzothiadiazole (BT) is regulated by thiophene (TP) and polycyclic aromatic hydrocarbons [naphthalene (N) and anthracene (A)], and series of polymers including B-BT-TP-x, N-BT-TP-x and A-BT-TP-x (x = 0.2, 0.4, 0.6, 0.8) are synthesized. After thiophene and polycyclic aromatic hydrocarbon regulation, the polymers exhibit strong absorption in the whole visible light region of 400->650 nm and quick internal charge separation and transfer. Visible-light-driven photocatalytic hydrogen production rates of the synthesized polymers follow the order of B-BT (170.0 μmol/h) < B-BT-TP-0.6 (735.3 μmol/h) < N-BT-TP-0.4 (841.5 μmol/h) < A-BT-TP-0.6 (969.2 μmol/h) using 30 mg catalyst with 1.0 wt% Pt as cocatalyst. In addition, high apparent quantum yield (AQY) values of 8.04%, 5.58% and 0.95% under 550 nm, 650 nm and 700 nm monochromatic lights are obtained using A-BT-TP-0.6 catalyst. The present work provides new insights into design of advanced organic semiconductors for highly efficient photocatalytic solar energy conversion.

Construction of Type-II Heterojunctions in Crystalline Carbon Nitride for Efficient Photocatalytic H2 Evolution.

As an encouraging photocatalyst, crystalline carbon nitride (CCN) exhibits unsatisfactory photocatalytic activity and stability due to its rapid recombination of photo-generative carriers. Herein, high-crystalline g-C3N4 was prepared, including CCN obtained in KCl (K-CCN), LiCl-KCl mixture (Li/K-CCN), and LiCl-NaCl-KCl mixture (Li/Na/K-CCN), via the molten salt strategy using pre-prepared bulk carbon nitride (BCN) as a precursor. The obtained BCN sample was formed by heptazine-based units, which convert into triazine-based units for K-CCN. Heptazine and triazine are two isotypes that co-exist in the Li/K-CCN and Li/Na/K-CCN samples. Compared with BCN and other CCN samples, the as-prepared Li/Na/K-CCN sample exhibited the optimal photocatalytic hydrogen evolution rates (3.38 mmol·g-1·h-1 under simulated sunlight and 2.25 mmol·g-1·h-1 under visible light) and the highest apparent quantum yield (10.97%). The improved photocatalytic performance of the Li/Na/K-CCN sample is mainly attributed to the construction of type-II heterojunction and the institution of the built-in electric field between triazine-based CCN and heptazine-based BCN. This work provides a new strategy for the structural optimization and heterostructure construction of crystalline carbon nitride photocatalysts.

Tungsten Oxide-Based Z-Scheme for Visible Light-Driven Hydrogen Production from Water Splitting.

The stoichiometric water splitting using a solar-driven Z-scheme approach is an emerging field of interest to address the increasing renewable energy demand and environmental concerns. So far, the reported Z-scheme must comprise two populations of photocatalysts. In the present work, only tungsten oxides are used to construct a robust Z-scheme system for complete visible-driven water splitting in both neutral and alkaline solutions, where sodium tungsten oxide bronze (Na0.56WO3-x) is used as a H2 evolution photocatalyst and two-dimensional (2D) tungsten trioxide (WO3) nanosheets as an O2 evolution photocatalyst. This system efficiently produces H2 (14 μmol h-1) and O2 (6.9 μmol h-1) at an ideal molar ratio of 2:1 in an aqueous solution driven by light, resulting in a remarkably high apparent quantum yield of 6.06% at 420 nm under neutral conditions. This exceptional selective H2 and O2 production is due to the preferential adsorption of iodide (I-) on Na0.56WO3-x and iodate (IO3-) on WO3, which is evidenced by both experiments and density functional theory calculation. The present liquid Z-scheme in the presence of efficient shuttle molecules promises a separated H2 and O2 evolution by applying a dual-bed particle suspension system, thus a safe photochemical process.