H2 Production Rate Research Articles

Synergistic effect and role of light for efficient photothermocatalytic CO2 reduction by CH4 on Pd/Co-Al1Mg3Ox

Photothermocatalytic CO2 reduction by CH4 converts greenhouse gases into valuable syngas, but limited by high light intensity and carbon deposition. Here, we designed a nanocomposite supporting low content of Pd nanoparticles on Co and Al doped MgO (Pd/Co-Al1Mg3Ox), achieving high production rates of H2 (rH2, 73.04 mmol min−1 g−1) and CO (rCO, 84.80 mmol min−1 g−1) with light-to-fuel efficiency (η, 25.3 %) at relatively low light intensity (81.1 kW m−2). Compared to Pd/Al1Mg3Ox, Pd/Co-Al1Mg3Ox demonstrates improvements of rH2, rCO and η by 6.5, 6.2 and 6.7 times respectively with great durability of 48 hours. This originates from a synergetic effect between Pd and Co-Al1Mg3Ox that the participation of active oxygen from Co-Al1Mg3Ox greatly accelerates carbon species (C*) oxidation. Interestingly, light plays unique roles on Pd/Co-Al1Mg3Ox which not only expedites C* oxidation, activates the oxygen connected to Pd and Co-Al1Mg3Ox, but also reverses rapid thermocatalytic deactivation by boosting CO desorption.

A novel hexagonal prism of Zr-based MOF@ZnIn2S4 core−shell nanorod as an efficient photocatalyst for hydrogen evolution

Photocatalytic water splitting is a commonly used pathway for hydrogen (H2) production, and it is crucial to develop highly active ZnIn2S4 (ZIS)-based photocatalytic systems. In recent years, metal-organic frameworks (MOFs) are also of great interest in the fields of energy production and environmental remediation. Therefore, this study primarily focuses on the fabrication of a series of heterojunction hexagonal prism-shaped Zr-based MOF@ZIS core-shell nanorods through a simple solvothermal method, in which ZIS nanosheets are highly distributed on the surface of the Zr-based MOF (NU-1000). The photocatalytic activities of the resulting materials were evaluated under visible light illumination (λ ≥ 400 nm) by combining different contents of NU-1000 with ZIS. The H2 evolution results demonstrate that the optimal content of NU-1000 corresponds to a photocatalytic H2 production rate of 8.53 mmol g−1 h−1, which is 5.3 times higher than that of pure ZIS. The enhanced photocatalytic activity of the NU-1000@ZIS (NUZ) heterojunction can be attributed to the incorporation of the NU-1000, which provides abundant active sites due to its larger specific surface area. Additionally, the well-matched band structure between the NU-1000 and ZIS is beneficial to efficiently transfer and separate the photogenerated charge carriers. Furthermore, the NUZ core-shell nanorods exhibit excellent stability, offering a new approach for the fabrication of composite photocatalysts by combining MOF-based and ZIS in the field of photocatalytic H2 production.

Eliminating interface shielding effect endowed by piezoelectric polarization in S-scheme heterojunction for high-efficiency H2 evolution

Eliminating the interface shielding effect within step-scheme (S-scheme) heterojunctions which can attenuate the separation driving force of built-in electric field plays a vital role in enhancing the photocatalytic performance. Herein, an extra driving force induced by piezoelectric field is introduced to mitigate such predicament in S-scheme, thereby facilitating the charge separation. Specifically, the piezoelectric CuInS2-BiFeO3 S-scheme heterojunction which with powerful piezoelectric field endowed by the piezoelectric BiFeO3 is constructed via a facile electrostatic self-assembly strategy and served as the touchstone to verify that hypothesis. The direction of built-in field between the heterojunction interface that is orienting from CuInS2 to BiFeO3 has been confirmed by in-situ X-ray photoelectron spectroscopy and electron paramagnetic resonance. Furthermore, the obviously piezo-field at the interface of CuInS2-BiFeO3 which can tilt energy band to enhance the built-in field under external force is also revealed by piezoresponse force microscopy. Consequently, benefiting from the highly-efficient charge separation offered by the synergy of piezoelectric field and S-scheme built-in electric field, a remarkably H2 production rate of 1465.1 µmol/g is achieved under simultaneous visible light and ultrasonic vibration irradiation. This work sheds light on the role of external field in enhancing the efficient separation of carriers in S-scheme heterojunctions.

Piezoelectric field accelerating charge transfer in Z-scheme heterojunction 2D-KNbO3/1D-CdS for efficient piezo-photocatalytic H2 evolution and TCH degradation

The piezo-phototronic effect utilizes the piezoelectric polarization field to tune the photogenerated carrier separation and transport performance in heterojunctions, which portrays a promising strategy for addressing energy shortage and environmental pollutants. Herein, a novel Z-scheme piezoelectric semiconductor heterojunction, 2D-KNbO3/1D-CdS-x (KNCS-x), was fabricated using hydrothermal and solvothermal methods, resulting in enhanced redox capacity. Under the simultaneous light and strain, KNCS-15 exhibits the highest piezo-photocatalytic activity, with degradation rates of tetracycline hydrochloride degradation rate constant, H2O2 as well as H2 production rates being 1.806 × 10−2s−1, 45.56 mM·h−1·g−1 and 8.87 mmol·h−1·g−1, respectively, which are 1.4, 2.4 and 1.9 times of photocatalysis alone, and 9.8, 9.2 and 9.8 times of piezocatalysis alone. DFT calculations, EPR and PALS indicate that the Z-scheme structure realizes effective separation of electron-hole pairs with strong redox ability and a higher carrier concentration. The enhanced catalytic activity is attributed to the introduction of piezoelectric potential, which facilitates improved spatial separation of electrons with high reduction and holes with high oxidation potential.

Impact of Dual Functionalities of Mo‐Doped BiFeO3 Decorated with Bi4MoO9 Heteroatoms for Piezo‐Photocatalytic Activity

AbstractPiezocatalysts have shown great promise for effcient hydrogen generation. However, their application is limited by the rapid charge recombination and sluggish charge transfer rate of piezo‐induced charge carriers. This work aims to address the preceding limitations by controlled synthesis of a representative piezocatalyst, BiFeO3 doped with Mo atoms and decorated with Bi4MoO9 (BMO) heteroatoms using sol‐gel method. The substitutional doping of Mo on BFO (BFMO) was shown to induce a shallow energy level near the conduction band that acted as a trapping state, to suppress recombination of charge carriers, enhance charge mobility for transport to the surface, modulate band alignment, and lower the energy barrier for surface reaction. The formation of BFMO/BMO heterostructures induced electrical band bending, leading to the electric potential gradient, hence promoting charge carrier separation and transfer. The BFMO/BMO with 0.5 mol % Mo (Mo‐5) demonstrated four times faster piezocatalytic Rhodamine B (RhB) dye degradation rate (k of 0.032 min−1) compared to pristine BFO (0.009 min−1). Further, the Mo‐5 exhibited a 45% higher piezocatalytic H2 production rate (14.4 µmol/g/h) compared to pristine BFO (9.8 µmol/g/h) while being cocatalyst‐free. Coupling piezocatalysis with photocatalysis was found to reduceperformance relative to the individual processes, which is attributed to Auger recombination which impedes any potential synergistic effect.

Rational construction of N-containing carbon sheets atomically doped NiP-CoP nanohybrid electrocatalysts for enhanced green hydrogen and oxygen production

The pursuit of sustainable energy production has directed rigorous research in the field of electrocatalysis, particularly for water electrolysis (i.e., hydrogen (HER) and oxygen evolution reactions (OER)). This study discloses the rational synthesis of N-containing carbon sheets atomically doped NiP-CoP nanohybrid (NiP-CoP/NCS) via precipitation/calcination. The fabrication method tailored the physicochemical merits for collective contribution to improved green hydrogen and oxygen, elucidated by surface/bulk characterization and theoretical calculations. Thus, the NiP-CoP/NCS had improved HER activity at lower overpotential (ƞ10 = 197.7/274.6 mV), higher exchange current density (jo = 0.71/0.67 mA/cm2), turnover frequency (TOF = 2.63/1.47 s-1), H2 production rate (3601.63/2519.12 µmol/g/h) and superior stability after 24 h in acid/alkaline media, than NiP/NCS and CoP/NCS. Moreover, NiP-CoP/NCS delivered impressive OER activity at reduced ƞ10 (309.1 mV), and Tafel slope (ba = 58.9 ± 3.0 mV/dec), but higher TOF (3.67 s-1) and O2 production rate (3643.96 µmol/g/h) relative to NiP/NCS and CoP/NCS, besides higher stability for 24 h. These were further proved by theoretical calculations. This work indicates a deeper understanding of the fabrication methods of making efficient electrocatalysts for green and sustainable energy conversion.

Methanol steam reforming over copper supported on apatites

Low-temperature methanol steam (MSR) reforming over Cu is an efficient process for releasing H2 from this promising liquid hydrogen carrier but the Cu contents of commercial catalysts are often exceedingly high. Here we show that Sr-exchanged fluoro and hydroxyapatites with 1wt.% Cu exhibit very high methanol turnover frequencies up to 386h-1 and H2 production rates up to 6569mol H2 kgCu-1 h-1 with CO selectivity as low as ~0.25% at 250 °C. Formaldehyde and methyl formate are the only other byproducts which are especially observed over catalysts with low Sr/P ratio in the hydroxyapatite. The reforming proceeds through methoxy, formaldehyde and formate species according to in situ FTIR and mass spectrometric measurements. The spectroscopic analyses further reveal the involvement of apatitic HPO42- ions in the catalytic sequence. Thus, the catalytic synergy between Cu and apatites provides a basis for highly efficient, bifunctional MSR catalysts with low copper content.

Photocatalytic activity of molybdenum-doped LOS- zeolite for efficient dye degradation and hydrogen production

This research investigates the synthesis and application of Losod-zeolite (LOS-Z), a crystalline hydrated sodium aluminosilicate (Na12Al12Si12O48.xH2O) as a potential photocatalyst for dye degradation and H2 production from dye-degraded water. The photocatalytic properties are enhanced by impregnating molybdenum (Mo) into LOS-Z (Mo@LOS-Z). XRD, FTIR, SEM, EDX, and elemental mapping were used to study the physicochemical properties of synthesized materials while UV–vis and PL were employed to explore the optoelectronic properties. The photocatalytic activities for dye degradation and H2 production were evaluated using methylene blue (MB) under visible light irradiation. An enhancement in the efficiency of dye degradation (56%–82%) and H2 production rate was demonstrated due to the competitive photocatalytic performance of 10% Mo@LOS-Z compared to the pristine LOS-Z and CFA-BFA blend. It exhibited 2.5 times higher (∼1200 μmol g−1h−1) H2 production than the LOS-Z (∼480 μmol g−1h−1) due to the synergistic effects of narrowed band gap and recombination rate. This study could pave the way forward into the synthesis of waste-derived photocatalysts for efficient dye degradation and H2 production.

Construction of Bi5O7I/Bi3O4Br heterojunction with abundant oxygen vacancies to enhance photocatalytic performance

The low separation efficiency of photogenerated charge carriers is the main impediment to the practical application of photocatalysis. Herein, Bi5O7I nanoparticles with abundant oxygen vacancies (DBOI) were deposited on Bi3O4Br nanosheets (BOBr) to create a novel 0D/2D DBOI/BOBr heterojunction (DBOI-Br) using a facile solution method. The structure of surface oxygen vacancies (SOVs) was demonstrated using HRTEM, low-temperature EPR, and XPS. The effective interface contact between DBOI and BOBr resulted in the establishment of an internal electric field (IEF) and band bending. The photogenerated charge transfer mechanism was validated through in situ irradiated XPS, work function calculation, and ERS measurement. The synergistic effect of IEF, band bending, and SOVs efficiently suppressed the recombination of photogenerated charge carriers, enhancing the photocatalytic activity. Almost 100% of tetracycline, oxytetracycline, levofloxacin, ciprofloxacin, methylene blue, and rhodamine B, as well as 92.3% of phenol, could be decomposed using DBOI-Br under visible light irradiation. The average production rates of H2, O2, and H2O2 were 805, 3800, and 562 μmol h-1 g-1 over 4h, corresponding to quantum efficiencies of 3.67%, 10.4%, and 5.26% at 420nm, respectively. This study introduces a new promising DBOI-Br heterojunction photocatalyst with rich SOVs to enhance the charge separation efficiency for various photocatalytic applications.

Pilot microbial electrolysis cell closes the hydrogen loop for hydrothermal wet waste conversion to jet fuel

The global shift toward net-zero emissions necessitates resource recovery from wet waste. In this study, we demonstrate the first feasibility of combining pilot-scale microbial electrolytic cells (MECs) with hydrothermal liquefaction (HTL) for simultaneous post-hydrothermal liquefaction wastewater (PHW) treatment and efficient hydrogen (H₂) production to meet biocrude upgrading requirements. Long-term single reactor operation revealed that fixed anode potential enabled rapid startup, and low catholyte pH and high salinity were effective in suppression of cathodic methanogenesis and acetogenesis – resulting in high current density of 16.6 A m−2 and 9.3 A m−2 when feeding synthetic wastewater and PHW respectively. Additionally, the anode biofilm exhibited spatial variations in response to local environmental conditions. Onsite parallel or serial operations of multiple MECs showed good performance using actual PHW with a record-high H2 production rate of 0.5 L LR day−1 for MEC over 10 liters scale, and the optimal chemical oxygen demand (COD)-to-H2 yield reached 0.127 kg-H2 per kg-COD, supporting a self-sufficient, closed-loop upgrade to jet fuel.

Improved hydrogen production in immobilized Chlamydomonas reinhardtii cells with inhibited inter-photosystem electron transfer

The production of molecular hydrogen (H2) by microalgae holds great promise, and immobilization techniques offer potential for further advancement in this field. The current study focuses on investigating the positive impact of immobilization on maintaining the stability and activity of photosystem II (PSII) over incubation time, with the aim of enhancing H2 production potential in green microalgae Chlamydomonas reinhardtii. For this purpose, immobilized cells within alginate beads were treated with small concentrations of 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB) inhibitor to induce the partial inhibition of inter-photosystem electron transport, recently reported as a novel approach for sustaining microalgal H2 production. A comparative analysis of fluorescence decay kinetic changes and EPR spectroscopy of the cell beads revealed the superior capacity of immobilization for sustaining PSII stability and activity in batch culture over time. Treatment of the cell beads with 3.5 μM DBMIB led to sustained H2 production yielding over 200 μmol H2/mg Chl within 3 weeks, with an average H2 production rate of approximately 10 μmol/mg Chl per day, both of which were roughly twice as high as those observed in free cells treated with DBMIB. Our findings underscore the significance of integrating immobilization with a proven and effective method for H2 production, thereby enhancing its sustainability and productivity.

Photocatalytic H2 production over CoxNi0.85-xSe decorated TiO2 S-scheme heterojunction

The construction of an S-scheme heterojunction facilitates the efficient separation of charges and preserves its high REDOX potential. In this study, a series of CoxNi0.85-xSe(x=0.05,0.1,0.2,0.3and0.4) and TiO2 nanoparticles were both prepared using solvothermal method, and then Co0.3Ni0.55Se was combined with TiO2 to form Co0.3Ni0.55Se/TiO2 heterojunction through a solvent evaporation strategy for efficient photocatalytic H2 production. It found that the H2 production rate of 10 wt%-Co0.3Ni0.55Se/TiO2 composite can reach 10,070.9 µmol∙g−1∙h−1 with TEOA as a sacrificial agent under a simulated sunlight irradiation, which is 307.9, 33.5and 3.3 times higher than those of pure Co0.3Ni0.55Se,TiO2 and 10 wt%-Ni0.85Se/TiO2, respectively. This enhanced performance is primarily attributed to the formation of an S-scheme heterojunction between TiO2 and Co0.3Ni0.55Se, which effectively enhances light absorption capacity and facilitates charge separation and migration during light irradiation processes. Especially, the S-scheme charge separation can retain the active REDOX capacity of electrons in the conduction band of CoxNi0.85-xSe and the holes in the valance band of TiO2, thereby promoting H2 generation. This study demonstrates that CoxNi0.85-xSe serves as a reducing photocatalyst that offers a viable approach for achieving ideal S-scheme heterojunctions.

WO3/g-C3N4 synergistic photocatalysts for degradation and H2 production

WO3/g-C3N4 composite samples were prepared using hydrothermal method. The photocatalytic activity was assessed by photocatalytic degradation and H2 production experiments. The experimental findings suggested that WO3/g-C3N4 (1:1) degraded 95 % of the MB in 50 min and produced H2 at a rate of 712.38 μmol⸱g−1⸱h−1, which was 10 times the H2 production rate of g-C3N4. The improved photodegradation and H2 production properties could be due to the increased specific surface area, improved photogenerated carrier separation efficiency, broadened visible light absorption range, increased photocurrent density, and reduced charge transfer resistance. Meanwhile, the synergistic effect of WO3 and g-C3N4 realizes the bifunctionality of degradation and H2 production. In addition, possible reaction mechanisms of WO3/g-C3N4 composite samples in photodegradation and H2 production were proposed.

Enhanced solar-powered H2 production from water splitting and sustainable wastewater treatment using interface-engineered ZnIn2S4/TiO2/Ti3C2 S-scheme heterocatalyst

Developing efficient photocatalysts that can degrade persistent antibiotics in water bodies and generate clean H2 through water splitting is crucial for environmental and energy sustainability. This study introduces an advanced hierarchical ZnIn2S4/TiO2/Ti3C2 (ZIS/TO/TC) heterocatalyst for the efficient removal of amoxicillin (AXC) from wastewater and the production of H2 through water reduction process under simulated solar illumination. The ZIS/TO/TC hybrids were fabricated via an in situ hydrothermal process, resulting in a hierarchical 3D structure that capitalizes on the complementary properties of each component. The design of the S-scheme heterojunction significantly enhances charge separation and transfer efficiency, offering improvements over traditional type-II or Z-scheme mechanisms. Notably, the optimized ZIS10/TO/TC hybrid catalyst demonstrated remarkable activity, achieving 100 % AXC degradation and excellent mineralization within 90 min, along with an H2 production rate of 4104 μmol h−1 g−1, significantly outperforming the individual components and exceeding previously reported efficiencies. The outstanding performance of the ZIS10/TO/TC hybrid is attributed to its enhanced light absorption properties, synergistic interactions among the ZIS, TO, and TC MXene, and the efficient S-scheme charge transfer mechanism, which facilitates effective charge separation and transfer while preserving the strong reducing and oxidizing capabilities of the components. Additionally, the ZIS10/TO/TC hybrid exhibited excellent stability over multiple photocatalytic tests, emphasizing its potential for practical applications. Therefore, this research demonstrates an advanced and highly efficient hybrid photocatalyst that offers a promising and sustainable solution for both integrated water treatment and renewable energy generation.

Dynamic Reconstruction of Yttrium Oxide-Stabilized Cobalt-Loaded Carbon-Based Catalysts During Thermal Ammonia Decomposition.

Hydrogen production from the decomposition of ammonia is considered an effective approach for addressing challenges associated with hydrogen storage and transportation. However, their relatively high energy consumption and low efficiency hinder practical multi-scenario applications. In this study, Y2O3-stabilized catalysts with Co-loaded onto porous nitrogen-doped carbon (Y2O3-Co/NC) are synthesized by pyrolysis of Y(NO3)3-modified ZIF-67 under an inert atmosphere, followed by annealing in a reducing environment. The introduction of Y2O3 enhanced the recombination and desorption of N atoms and facilitated the gradual dehydrogenation of NHx on the catalyst surface, resulting in improved catalytic activity for the thermal decomposition of ammonia. Benefitting from the electron-donating properties of Y2O3 and N-doped carbon, the optimized catalyst achieved a remarkable NH3 conversion efficiency of 92.3% at a high gas hourly space velocity of 20000 cm3· ·h-1 with an encouraging H2 production rate of 20.6 mmol· ·min-1 at 550°C. Moreover, the synthesized catalyst undergoes a fast-dynamic reconstruction process, resulting in exceptionally stable catalytic activity during the thermal decomposition of ammonia, rendering it a promising candidate for carbon-free energy thermocatalytic conversion technology.

MoS2/CuS/g-C3N4 double S-scheme with charge storage ability for efficient photocatalytic H2 production

The photocatalytic H2 production technology exhibits promising potential in addressing the challenges of environmental pollution and energy crisis. In this work, CuS particles decorated MoS2 seaweed spheres (MoS2/CuS) were synthesized through a hydrothermal method, then they are loaded on the surface of g-C3N4 nanosheets using a solvent evaporation strategy to form MoS2/CuS/g-C3N4 double S-scheme heterojunction. The investigation reveals the H2 production rate of 25 wt% MoS2/CuS/g-C3N4 can reach up to 1438 μmol·g-1·h-1, which is 14.8-fold of g-C3N4 (97 μmol·g-1·h-1). Further studies indicate that the introduction of MoS2/CuS can broaden the light absorption range, increase electrochemical specific surface area, reduce the activation energy for H2 production and increase hydrophilicity of the composite. Especially, CuS can suppress carrier recombination effectively through its electron storage and release ability. Based on the experimental and theoretical analysis of band structures, the charge transfer in MoS2/CuS/g-C3N4 shares optimized double S-scheme charge transfer pathways with a dual reduction site, leading to an enhanced H2 evolution kinetics. This work offers valuable insights for the advancement of novel double S-scheme heterojunctions, showcasing their potential in energy storage and photothermal enhancement effects.

Plasma-assisted NH3 cracking in warm plasma reactors for green H2 production

NH3 is emerging as a carrier of green H2, but it requires a green and economical NH3 cracking process based on renewable energy. Plasma technology is promising for this purpose, as it can crack NH3 without the need for a catalyst and is highly compatible with renewable electricity, reducing the environmental footprint of the cracking process. This work investigates the NH3 cracking performance of four different warm plasma reactors with different configurations and operating in a wide range of conditions. We show that the NH3 conversion in warm plasma reactors is primarily determined by the specific energy input, with the main difference observed in the energy cost (EC) of cracking. The lowest EC obtained is 146 kJ/mol but at a conversion of only 8 %. A more reasonable conversion of around 50 % yields an EC of around 200 kJ/mol in two of the reactors investigated. Plasma reactors operating at higher feed flow rates are more efficient and yield a higher H2 production rate. Our data indicate that NH3 cracking in these warm plasma reactors occurs mainly via thermal chemistry, with non-thermal plasma chemistry playing a less prominent role. NH3 decomposes not only inside the plasma core but also in a hot volume around it, which reduces the EC. Our study shows that warm plasmas are significantly more efficient for NH3 cracking than cold plasmas, even when the latter are combined with catalysts.

Tuning Electronic and Proton Transfer Properties on Amino-Functionalized Co-Based MOF for Efficient Photocatalytic Hydrogen Evolution.

Efficient hydrogen (H2) production through photocatalytic water splitting was achieved by using an amino-functionalized azolate/cobalt-based metal-organic framework (MOF). While previous reports highlighted the amino group's role only as a substituent group for enabling light absorption of MOFs in the visible region, our present study revealed its dual role. The amino substituent not only acts as an electron donor to increase the electron availability at the active Co sites but also provides hydrogen-hopping sites within the pore channel, facilitating proton (H+) diffusion along the framework. This dual functionality significantly boosts the performance of this Co-MOF as a hydrogen evolution cocatalyst. When combined with fluorescein and triethylamine as the photosensitizer and sacrificial agent, respectively, the Co-MOF achieved a remarkable H2 production rate of 27 mmol g-1 over 4 h. Notably, this performance surpasses those of benchmark platinum (Pt) and titanium dioxide (TiO2) cocatalysts.

Enhanced Piezocatalytic Water Splitting by Platinum‐Decorated Barium Titanate

AbstractPiezocatalysis has emerged as a promising field of research that uses mechanical energy to drive a chemical change. There is growing evidence that piezocatalysts can perform challenging chemical conversions from organic transformations to water splitting. A key challenge to piezocatlaysis is mitigating the inherent high relative permittivity of a ferroelectric material. This high permittivity restricts the transfer of carriers required for a chemical reaction to occur and reduces the reaction rate. Here the concept of producing a co‐catalyst system is taken to enhance carrier mobility increasing the observed reaction rate. The study highlights the importance of determining the sonochemical and piezocatalytic contributions to catalysis. The combination of a Pt metal co‐catalyst with BaTiO3 through a simple solid‐state method led to a four fold increase in the rate of H2 production compared to BaTiO3 and sonochemical reactions in the absence of a catalyst. BaTiO3/Pt is found to exhibit stable piezocatalytic performance over 12 h. Where there is a deviation from steady‐state water splitting, it is shown that this is due to mechanical removal of Pt rather than a phase change in the catalyst system. This work confirms the additive benefits of hybrid materials for improving piezocatalytic processes.

Cu2WS4 with high-exposure {0 0 1} surfaces promotes efficient charge separation in ZnIn2S4

The spatial segmentation of photogenerated carriers is crucial for achieving efficient photocatalytic H2 production (PHP) rates in photocatalyst. Design studies of crystalline catalyst facets and selective morphology control can facilitate the development of catalysts that expose more advantageous active facets. Herein, Cu2WS4/ZnIn2S4 composites are constructed by growing ZnIn2S4 nanosheets in situ on Cu2WS4 with largely exposed {001} surface. Experiments and density functional theory calculations demonstrate that the electrons of ZnIn2S4 flowed to the {001} surface of Cu2WS4, and the holes vectorially migrated to the {101} surface, during the reaction process, resulting in efficient spatial separation of the photogenerated carriers. The Cu2WS4/ZnIn2S4 achieves a PHP rate of 23.67 mmol g−1 h−1, 13.44-fold increase compared with pure ZnIn2S4. This report combines the advantages of the high-energy activity of the Cu2WS4 {001} surface to morphologically control the ratio of the {001}/{101} surfaces so that ZnIn2S4 can contact a larger area of the {001} surface. Furthermore, under the influence of crystallographic effects on the {001} and {101} surfaces, electrons and holes of ZnIn2S4 are transferred to different crystalline facets, promoting the redox reaction. This paper provides effective ideas for the rational design of photocatalysts with efficient carrier space separation.