Boosted photogenerated carriers separation in Z-scheme Cu3P/ZnIn2S4 heterojunction photocatalyst for highly efficient H2 evolution under visible light

Developing low-cost, highly efficient and robust photocatalystic hydrogen evolution system is a promising solution to environmental and energy crisis. Herein, a Z-scheme Cu₃P/ZnIn₂S₄ heterojunction photocatalyst was successfully constructed for the first time via a facile solution-phase hybridization method. The optimized Cu₃P/ZIS composite exhibited the highest H₂ production rate of 2561.1 μmol g⁻¹ h⁻¹ under visible light irradiation (>420 nm), which was 5.2 times greater than that of bare ZnIn₂S₄ and even exceeded the photocatalytic performance of Pt/ZIS composite. The apparent quantum yield of 10 wt% Cu₃P/ZnIn₂S₄ can reach 22.3% at 420 nm. The huge boost of photocatalytic hydrogen evolution activity is ascribed to the formation of heterojunction with the built in electric field within Cu₃P/ZnIn₂S₄ and Z-scheme charge carriers transfer pathway, which result in efficient separation and migration of charge carriers. In addition, both experimental and theoretical calculation confirmed that the charge-carriers transfer pathway of Cu₃P/ZnIn₂S₄ photocatalyst follows the Z-scheme mechanism instead of conventional type-Ⅱ heterojunction mechanism. This work is considered helpful for getting a great deal of insight into constructing high-activity and cost-effective transition metal phosphides (TMPs) based photcatalytic hydrogen production system and rationally designing Z-scheme heterojunction photocatalyst.     

Surface oxygen vacancy facilitated Z-scheme MoS2/Bi2O3 heterojunction for enhanced visible-light driven photocatalysis-pollutant degradation and hydrogen production

An oxygen-vacancy rich, bismuth oxide (Bi₂O₃) based MoS₂/Bi₂O₃ Z-scheme heterojunction catalyst (2-BO-MS) was prepared in an autoclave hydrothermal method using ethanol and water. The performance of MoS₂/Bi₂O₃ catalyst was examined for photocatalytic hydrogen evolution, photoelectrochemical activity, and crystal violet (CV) dye degradation by comparing with pristine Bi₂O₃ and MoS₂. The hydrogen evolution performances of 2-BO-MS catalyst exhibited 3075.21 μmol g⁻¹ h⁻¹, which is 7.18 times higher than that of MoS₂ (428.14 μmol g⁻¹ h⁻¹). The XPS, XRD and HRTEM analyses covered that the superior photocatalytic performance of 2-BO-MS catalyst might have stemmed out due to the existence of oxygen vacancies, enhanced strong interfacial interaction between MoS₂ and Bi₂O₃ and specific surface area. The in-depth investigation has been performed for MoS₂/Bi₂O₃ Z-scheme heterojunction using several characterization techniques. Moreover, the photocatalytic mechanism for hydrogen evolution and photodegradation were proposed based on trapping experiment results. This results acquired using MoS₂/Bi₂O₃ Z-scheme heterojunction would be stepping stone for developing heterojunction catalyst towards attaining outstanding photocatalytic activity.     

Preparation of direct Z-scheme Bi2WO6/TiO2 heterojunction by one-step solvothermal method and enhancement mechanism of photocatalytic H2 production

Direct Z-scheme Bi₂WO₆/TiO₂ heterojunction photocatalyst was prepared by one-step solvothermal method. The catalyst was characterized by XRD, TEM, XPS, UV–Vis DRS, photoluminescence spectroscopy and photoelectrochemical studies. The photocatalytic hydrogen production experiments show that Bi₂WO₆ did not generate H₂ and the H₂-production rate of TiO₂ is only 0.1 mmol⋅g⁻¹h⁻¹. The hydrogen production rate of the Bi₂WO₆/TiO₂ heterojunction photocatalyst reaches 12.9 mmol⋅g⁻¹h⁻¹, which is 129 times that of TiO₂. Compared with TiO₂, the enhanced H₂-production activity of the heterojunction catalyst can be attributed to the wider light absorption range and the efficient separation and migration of carriers at the close contact interface between Bi₂WO₆ and TiO₂. Based on the work functions of Bi₂WO₆, TiO₂ and their heterojunctions, combined with the results of electron paramagnetic resonance spectroscopy and Mott-Schottky measurements, the photocatalytic H₂ production mechanism of Z-scheme heterojunction Bi₂WO₆/TiO₂ was proposed. This work provides an easy and simple way to design a binary Z-scheme photocatalyst with efficient catalytic H₂-production activity without electron mediators.     

CdS-dots decorated WO3 nanorods photocatalyst with highly ordered interfacial structure for enhanced photocatalytic activities via Z-scheme mechanism

Constructing heterostructure is regarded as one of the most promising strategies for the enhancement of photocatalytic activities, because it can make charge carriers separated more efficiently at the interface. Herein, CdS-WO₃ heterostructure photocatalysts with highly ordered and intimate interfacial structure between the two constituent phases have been successfully prepared via a heterogeneous nucleation and growth of CdS nanoparticles on the surface of WO₃ nanorods, which were fulfilled through a controlled release of S^2? in the aqueous solution containing Cd²⁺ by the reaction of NH₃ with thioacetamide. The as-prepared photocatalysts were carefully studied in morphology and interfacial structure by FESEM and HRTEM, along with the other characterizations by XRD, XPS, and UV–visible absorption spectra. Under the irradiation of mercury lamp, the photocatalyst with 6 wt% CdS could afford a degradation rate of methyl orange (MO) of 94.6% in 70 min, 5.84 and 2.51 times as high as WO₃ and CdS, through a photocatalytic degradation process mainly controlled by·O₂^? as active species. In view of the distinctive alignment of energy bands of CdS-WO₃, the enhanced photocatalytic activities should be attributed to the more efficient Z-scheme mechanism that allows the photogenerated holes in WO₃ and electrons in CdS to function more efficiently thanks to the efficient interfacial recombination of the electrons in WO₃ and holes in CdS.     

CuWO4 as a novel Z-scheme partner to construct TiO2 based stable and efficient heterojunction for photocatalytic hydrogen generation

Synthesis of highly efficient, stable, visible active CuWO₄ nanoparticles through a simple methodology, paves a feasible path for enhancing the efficiency of TiO₂. A novel nanocomposite of CuWO₄ NP loaded TiO₂ NR heterojunction was mounted through a direct Z-scheme mechanism. Optimized composite CWT-3, advances the photocatalytic hydrogen production rates of TiO₂ to 106.7 mmol h^?1 g^?1_cat. CuWO₄ incorporation as OEP compensates inefficiency of WO₃ and other Z-scheme combinations reported so far, on limiting the charge carrier recombination followed by the generation of a greater number of excitons. Specific amounts of catalyst loading, study on the effect of sacrificial reagents, and understanding the effect of the light source, are the three pivotal steps that helped here to hamper the density of overall back reactions. The formation of Z-scheme heterojunction was evidently confirmed on determining the position of CBM and VBM, PL and photoelectrochemical analysis. Recyclability studies further proved the stable and efficient outcomes of CWT-3 for five consecutive cycles. Based on photocatalytic activity, employing BDF by-product glycerol as an optimized sacrificial reagent serves the oxidation demands and triggered 53.26% solar to hydrogen conversion efficiency under natural sunlight irradiation.     

A novel direct Z-scheme heterojunction of CoTiO3/ZnIn2S4 for enhanced photocatalytic H2 evolution activity

The shortage of fossil energy has become a growing global concern. It is particularly important to make full use of the infinite solar energy resources, and transform them into sustainable and clean energy. The development of hydrogen energy has become a feasible solution to solve the energy shortage problem. The preparation of photocatalysts featuring efficient charge transfer channels and high hydrogen production activity provides a pathway for the development of hydrogen energy. In this paper, we report for the first time the direct assembly of 2D ZnIn₂S₄ (ZIS) nanosheets on the surface of CoTiO₃ (CTO). The synthesized CoTiO₃/ZnIn₂S₄ (CTO/ZIS) photocatalyst features a direct Z-scheme charge transfer channel, which enhances the separation rate of photogenerated carriers, and accelerates the photocatalytic H₂ evolution (PHE) rate. Without the assistance of any co-catalyst, the PHE rate of prepared CoTiO₃/ZnIn₂S₄ was as high as 5.21 mmol g^?1 h^?1. Moreover, the H₂ evolution rate of CoTiO₃/ZnIn₂S₄ almost did not decrease significantly after four consecutive 4 h cycles. This investigation provides a valuable approach for the exploitation of novel and efficient Z-scheme photocatalysts in the application of solar energy to hydrogen energy conversion.     

Role of CTF in Bi2WO6/ZnO photocatalysts for effective degradation and hydrogen energy evolution

Energy crisis and water pollution are two serious threats to modern society. To overcome these problems a novel 3D-CTF@Bi₂WO₆/ZnO photocatalyst was prepared by using a hydrothermal method. Various techniques including XRD, SEM, UV-vis, BET and PL were used to analyze the crystallinity, morphology, structure, surface area and optical properties of the synthesized materials. The efficacy of the synthesized photocatalysts were evaluated by degrading the norfloxacin, sulfamethoxazole and by producing hydrogen gas through photocatalytic water splitting. The enhanced photocatalytic activity was due to the 3D structure of the material and synergy of the multicomponent system which also increased the separation of charge carriers. The Bi₂WO₆ has degraded the norfloxacin 55.21%, and 61.5% sulfamethoxazole in 90 min. The hybrid composite CTF@Bi₂WO₆/ZnO achieved the degradation rates of 85% for norfloxacin and 84% for sulfamethoxazole in the presence of LED light for 90 min which is much higher than the pure composite. Similarly, hydrogen evolution by using Bi₂WO₆ was 41/mmol/h⁻¹g⁻¹ and CTF@Bi₂WO₆/ZnO produced 387.9/mmol/h⁻¹g⁻¹ hydrogen. The prepared hybrid photocatalyst showed excellent photocatalytic activity and hydrogen production efficiency in a short period of time. So, the 3D-CTF@Bi₂WO₆/ZnO hybrid photocatalyst can be used in further photocatalytic applications.     

Photo-assisted electrolysis of urea using Ni-modified WO3/g-C3N4 as a bifunctional catalyst

Urea splitting to produce H₂ is as an energy-saving alternative to water electrolysis. However, efficient catalysts are required for the practical implementation of urea splitting because of the high overpotentials of the urea oxidation reaction and the hydrogen evolution reaction. Herein, a Ni-modified direct Z-scheme photocatalyst for the urea oxidation and hydrogen evolution reactions was synthesized by electroplating a WO₃/g-C₃N₄ nanocomposite on Ni-decorated carbon felt (WO/CN–Ni@CF). The 2D/2D nanostructure of the as-synthesized WO₃/g-C₃N₄ composite was confirmed by SEM and TEM. The WO/CN–Ni@CF catalyst electrode exhibited excellent bifunctional photocatalytic activity for the urea oxidation and hydrogen evolution reactions. Consequently, the potential required to generate 100 mA cm^?2 in an illuminated photoelectrochemical cell using WO/CN–Ni@CF as the anode and the cathode was reduced from 1.80 to 1.50 V. The photoelectrochemical cell exhibited good stability for 18 h with stable H₂ generation.     

Facile approach for Z-scheme type Pt/g-C3N4/SrTiO3 heterojunction semiconductor synthesis via low-temperature process for simultaneous dyes degradation and hydrogen production

The platinum/graphite-like carbon nitride/strontium titanate (Pt/g-C₃N₄/SrTiO₃) heterojunction semiconductor was synthesized using a facile approach for simultaneous photocatalytic dye degradation and hydrolysis of hydrogen production from simulated dyeing wastewater. Using SrTiO₃, trace Pt, and the addition of an appropriate amount of electron donors, it can effectively absorb sunlight and achieve 93% dye degradation and 471 μmol h⁻¹ g⁻¹ hydrogen yield. The analysis result indicates that the semiconductor is a Z-scheme type composite. It was also showed that the addition of electron donors effectively promoted the degradation rate, whereas the addition of Pt changed the photocatalytic reaction pathway, which resulted in a reduced degradation rate and a significant improvement of hydrogen evolution. A reaction mechanism for this phenomenon is also proposed.     

Phase controlled synthesis and the phase dependent photo-and electrocatalysis of CdS@CoMo2S4/MoS2 catalyst for HER

Herein we report a heterostructure with ultrathin nanosheets of Co-doped molybdenum sulfide on CdS nanorod array (donated as CdS@CoMo₂S₄/MoS₂) by hydrothermal synthesis. Firstly, elemental Co doping MoS₂ (CoMo₂S₄) delivers the double benefits of increased active sites and enhanced conductivity. Secondly, the structural characteristics maximally exposes the MoS₂ edges and enlarges interfacial contact area between the composite catalyst and electrolyte, as well as the efficient interfacial charge transfer. The ratio of CoMo₂S₄/MoS₂ in CdS@CoMo₂S₄/MoS₂ plays a crucial role for the enhanced photo-assistant electrocatalytic hydrogen evolution reaction (HER). We can tune the ratio of CoMo₂S₄/MoS₂ by controlling the preparation time or the ratio of precursor of Co/Mo. The catalyst with predominant MoS₂ phase shows superior photocatalytic HER performance with a high H₂ production rate of 46.60 μmol mg⁻¹ h⁻¹. Meanwhile, the catalyst with predominant CoMo₂S₄ phase exhibits not only relatively low overpotential of 172 mV at 10 mA cm⁻², which outperforms most values that have been reported on catalyst supported on ITO substrate, but also possesses H₂ production rate of 23.47 μmol mg⁻¹ h⁻¹. The superior photo-assistant electrocatalytic HER activity results from the synergistically structural and electronic modulations, as well as the proper energy band alignment between MoS₂ and CdS. This investigation could provide an approach to integrate the electro- and photocatalytic activities for HER, especially the photo responding behaviour at a bias potential which is meaningful to produce H₂ for actual application.     

Enhanced photocatalytic hydrogen evolution over 0D/3D NiTiO3 nanoparticles/CdIn2S4 microspheres heterostructure photocatalyst

Constructing S-scheme heterojunction is regarded as an effective mode to motivate excellent photocatalytic performance for hydrogen generation. This paper prepares NiTiO₃/CdIn₂S₄ S-scheme heterostructure photocatalyst by hydrothermal method successfully. In the experiments, 20 wt% NiTiO₃/CdIn₂S₄ has the supreme photocatalytic activity with the H₂ generation rate of 5168.6 μmol g⁻¹ h⁻¹ and the apparent quantum yield (AQY) of 5.14% at 420 nm, approximately 7.7 times of pure CdIn₂S₄. Through the phase characterization analyses, NiTiO₃ and CdIn₂S₄ successfully compounded, with NiTiO₃ nanoparticles wrapping around CdIn₂S₄ microspheres to form the irregular clumps. Further analyses of performance reveal the larger specific surface area, wider absorption region, faster charge transfer rate, outstanding photostability and recyclability for 20 wt% NiTiO₃/CdIn₂S₄, all of which play the significant role in photocatalytic hydrogen evolution activity. Finally, a plausible S-scheme photocatalytic mechanism for NiTiO₃/CdIn₂S₄ is proposed. This study provides a novel and effective S-scheme photocatalyst for hydrogen generation from water splitting.     

Electron transfer via a carbon channel for efficient Z-scheme solar hydrogen production

Z-scheme photocatalysis provides a promising solution to photocatalytic solar water splitting, yet restricted by inferior interfacial charge transfer. Here, we demonstrate a Z-scheme composite photocatalyst made of Fe₂O₃, a carbon layer, and g-C₃N₄ that can achieve efficient hydrogen generation from solar water decomposition. The success relies on in-situ preparation of core-shell Fe₂O₃@C structure at the surface of g-C₃N₄. Carbon as an intermediate layer thus acts as a bridge that significantly accelerates the migration of photogenerated electrons from Fe₂O₃ conduction band to g-C₃N₄ valence band. As a result, the highest rate of H₂ generation reaches 5.26 mmol h⁻¹g⁻¹. This activity is approximately 33-time greater than that achieved over pristine g-C₃N₄ and about 4-time larger than that obtained over a Fe₂O₃/g-C₃N₄ heterojunction without internal carbon layer. This work explicates the potential insight of the composite and paves a promising way to engineer the charge transfer behavior.     

Construction of Cu7.2S4/g-C3N4 photocatalyst for efficient NIR photocatalysis of H2 production

Graphite-like carbon nitride (g-C₃N₄) has been regarded as a promising photocatalyst for solar-to-chemical conversion. Nevertheless, the narrow absorption of light extremely limited its photocatalytic performance under near-infrared (NIR) irradiation. Herein, the Cu₇.₂S₄ with outstanding NIR absorption was successfully introduced to g-C₃N₄ nanosheets through a simple in-situ growth procedure. As expected, the constructed Cu_7.2S₄/g-C₃N₄ (CSCN) photocatalysts exhibit superior H₂ production activity of 82 μmol g⁻¹ h⁻¹ under NIR light irradiation (λ > 800 nm), which outperforms currently reported g–C₃N₄–based NIR-driven H₂ production systems. Especially, the optimal sample CSCN-5 displays a robust activity of 66 μmol g⁻¹ h⁻¹ at λ = 850 nm monochromatic light irradiation. The excellent photocatalytic performance is linked to the extended optical absorption as well as the efficient separation efficiency of photoinduced carriers, which are evidenced by the UV-visible absorption spectroscopy and photoelectrochemical test. This work provides an effective approach for constructing a Cu_7.2S₄/g-C₃N₄ photocatalytic system for the transformation of NIR solar energy into hydrogen.     

Unique ternary Cd0.85Zn0.15S@WO3/WS2 core-shell nanorods for highly-efficient photocatalytic H2 evolution under visible-light irradiation

Development of noble-metal-free photocatalysts for efficient solar-powered water-splitting is of great interest yet still challenging to date. In this work, unique ternary Cd_0.85Zn_0.15S@WO₃/WS₂ (CZ_0.15S@WO₃/WS₂) core-shell nanorods consisting of amorphous WO₃ and few-layered WS₂ nanosheets were synthesized through a two-step solvothermal method for the first time. The composition of WO₃/WS₂ shell is found to vary with the change of W content, which has a significant impact on the photocatalytic property of CZ_0.15S@WO₃/WS₂ toward H₂ evolution reaction (HER). Under visible-light irradiation (λ > 420 nm), the optimized CZ_0.15S@WO₃/WS₂ composite (n (WO₃): n (WS₂) = 3:1) demonstrates a superior HER activity of 76.33 mmol h⁻¹ g⁻¹ (corresponding to an AQY of 23.9% at 420 nm), which can be further remarkably increased to 157.29 mmol h⁻¹ g⁻¹ when the reaction is driven by full Xe-lamp spectrum. The HER capability of CZ_0.15S@WO₃/WS₂ is much better than that of Pt-decorated CZ_0.15S and most CdS-based photocatalysts ever reported, due to the notably enhanced charge transfer and separation via the synergistic cooperation of Z-scheme and type-I charge transfer processes. The findings displayed here could inspire new strategies to optimize the charge separation of multi-component photocatalysts for highly-effective solar conversion and utilization.     

An anti-symmetric dual (ASD) Z-scheme photocatalytic system: (ZnIn2S4/Er3+:Y3Al5O12@ZnTiO3/CaIn2S4) for organic pollutants degradation with simultaneous hydrogen evolution

An anti-symmetric dual (ASD) Z-scheme ZnIn₂S₄/Er³⁺:Y₃Al₅O₁₂@ZnTiO₃/CaIn₂S₄ photocatalyst was prepared by isoelectric point and calcination methods. The photocatalytic activity is estimated via degradation of Acid Orange II as a target organic contaminant with simultaneous hydrogen evolution under simulated solar-light irradiation. The prepared ASD Z-scheme ZnIn₂S₄/Er³⁺:Y₃Al₅O₁₂@ZnTiO₃/CaIn₂S₄ photocatalyst has a high photocatalytic activity, which can be assigned to the enlarged photoresponse range, increased reduction surface and enhanced separation efficiency of photo-induced carriers. Furthermore, the cyclic experiment proves that the prepared ASD Z-scheme ZnIn₂S₄/Er³⁺:Y₃Al₅O₁₂@ZnTiO₃/CaIn₂S₄ photocatalyst still maintains a high photocatalytic activity within five repetitive cycles. Moreover, the mechanism on photocatalytic degradation of organic pollutants with simultaneous hydrogen evolution caused by ASD Z-scheme ZnIn₂S₄/Er³⁺:Y₃Al₅O₁₂@ZnTiO₃/CaIn₂S₄ photocatalyst is proposed. It is wished that this study could provide a promising pathway for effective degradation and rapid hydrogen production.     

In-situ construction of direct Z-scheme sea-urchin-like ZnS/SnO2 heterojunctions for boosted photocatalytic hydrogen production

Constructing direct Z-scheme heterostructure is an effective way to promote the separation of photogenerated carriers and optimize the redox ability of the photocatalytic system. This work reports the in-situ synthesis of sea-urchin-like ZnS/SnO₂ Z-scheme heterojunctions via a one-step hydrothermal method. Both experimental results and density functional theory (DFT) calculations indicate that the tight interfaces derived from in-situ precursor dissociation can ensure a fast transfer for photogenerated carriers, meanwhile, the Z-scheme type of heterojunctions can increase the carrier separation efficiency and maintain the high reduction ability of photogenerated electrons. As expected, the photocatalytic hydrogen evolution rate of the as-optimized ZnS/SnO₂ sample can reach 2.17 mmol g^?1 h^?1, which is 15.5 times higher than that of the commercial ZnS. This work can offer a novel strategy for designing Z-scheme heterojunction as well as controlling the contact interface for boosted photocatalytic activity.     

Hierarchical ZnIn2S4: A promising cocatalyst to boost visible-light-driven photocatalytic hydrogen evolution of In(OH)3

Efficient separation of electrons and holes, associated with the reduction and oxidation, is of great importance in a photocatalytic reaction. 3D hierarchical core-shell-like ZnIn₂S₄@In(OH)₃ microspheres have been fabricated by a facile hydrothermal method via controlling the sulfur source. The marigold-like spherical ZnIn₂S₄ induced the in situ growth of cubic In(OH)₃ nanosheets as the outer shell, which efficiently transferred the photogenerated electrons and achieved efficient charge separation efficiency for highly photocatalytic H₂ production. Moreover, the intimate interfacial contact between ZnIn₂S₄ core and In(OH)₃ shell offered rectified charge transfer directions, which further boosted the charge separation. In consequence, the photocatalytic H₂ evolution under visible light irradiation was achieved on wide-gap In(OH)₃ owing to ZnIn₂S₄ as a cocatalyst, and a prominent photocatalytic H₂ production of 2088 μmol g⁻¹ was obtained on core-shell-like ZnIn₂S₄@In(OH)₃ structure with an apparent quantum efficiency of 1.45% (400 nm), which was nearly 2-folds higher of H₂ production rate than the pristine ZnIn₂S₄. This work provides a prototype material for high efficiency of hydrogen evolution, and gives a new insight for the development of efficient heterojunction photocatalysts.     

Photocatalytic hydrogen generation by WO3 in synergism with hematite-anatase heterojunction

The present study reports about exploration of a multi-component photocatalytic system comprising of WO₃, TiO₂ and Fe₂O₃ with tandem n-n heterojunctions. The ternary WO₃/TiO₂/Fe₂O₃ nanocomposite with WO₃ nanoparticles over the interfaces of Fe₂O₃ and TiO₂ is synthesized by wet precipitation followed by thermal decomposition. The WO₃/TiO₂/Fe₂O₃ nanocomposite has an enhanced photocatalytic performance towards hydrogen generation by water splitting reaction under visible light irradiation, when compared to the Fe₂O₃/TiO₂ system. A band gap of 2.10 eV, favouring visible light absorption was achieved with the distribution of WO₃ nanopartcles over the interfaces of Fe₂O₃ and TiO_2. The as prepared WTF heterojunction exhibited a maximum hydrogen production rate of 10.2 mL h⁻¹ for a catalyst loading of 0.025 g mL⁻¹. The enhanced photocatalytic performance is tested in presence of various sacrificial agents and proton source. In both cases, the higher photocatalytic efficiency is attributed to the more visible light harnessing ability and pronounced charge separation owing to the tandem n-n heterojunctions generated between TiO₂ with WO₃ and TiO₂ with Fe₂O₃ semiconductors and enhancing the lifetime of the photogenerated electron-hole pairs.     

Decoration of plasmonic Cu nanoparticles on WO3/Bi2S3 QDs heterojunction for enhanced photoelectrochemical water splitting

We report a WO₃/Cu/Bi₂S₃ wherein incorporation of Cu nanoparticles (Cu NPs) to enhance the photoelectrochemical activity over WO₃/Bi₂S₃. Cu NPs effectively harvest the light energy upon plasmon excitation and transfer the energy to contacted WO₃, thereby improving the photoelectrochemical (PEC) performance. The WO₃/Cu/Bi₂S₃ composite was characterized by scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and X-ray diffraction (XRD) to analyze the morphology and interfacial contact between the semiconductors. The photocurrent density and Solar-to-Hydrogen conversion efficiency for this composite is 10.6 mA cm⁻² at 1.23 V (versus RHE) and 3.21% at 0.81 V (versus RHE), which are much higher than WO₃/Bi₂S₃ with 4.02 mA cm⁻² at 1.23 V (versus RHE) and 2.46% at 0.81 V (versus RHE) respectively. Moreover, the stability and photo-response of WO₃/Cu/Bi₂S₃ were carried out through chronoamperometric studies. The composite retained its stability over 50 cycles without decay in PEC performance. High incident photon conversion efficiency (IPCE) value of about 51% is achieved which is evident from the high photocurrent density. Incorporation of Cu NPs increase the photoactivity which is evident from the photocurrent value. The increased activity of Cu NPs sandwiched composite is attributed for the quick electron transfer to semiconductor due to surface plasmon resonance (SPR) effect.     

ZnIn2S4 modified CaTiO3 nanocubes with enhanced photocatalytic hydrogen performance

Novel ZnIn₂S₄/CaTiO₃ nanocubes were prepared by a two-step method and used as a visible light photocatalyst for efficient hydrogen production. The control of the content of CaTiO₃ could effectively change the photocatalytic H₂ production activity of ZnIn₂S₄/CaTiO₃ nanocubes, and the maximum H₂ evolution amount reached to 133116.43 μmol g⁻¹ in 6 h. The photocatalytic hydrogen production efficiency of ZnIn₂S₄/CaTiO₃ nanocubes was almost 4.5 times higher than that of pure ZnIn₂S₄. The electrochemical impedance spectrum of ZnIn₂S₄/CaTiO₃ exhibited the smallest arc radius, time-resolved PL spectrum showed that the carrier lifetime of ZnIn₂S₄/CaTiO₃ nanocubes was 3.29 ns, and the photocurrent density of ZnIn₂S₄/CaTiO₃ reached to 0.81 μA cm⁻². The prepared ZnIn₂S₄/CaTiO₃ nanocubes increased visible light absorption, improved the separation and transfer of photo-generated electrons and holes, and inhibited the recombination of photo-generated electron-hole pairs. ZnIn₂S₄/CaTiO₃ nanocubes exhibited the enhanced photocatalytic activity and high stability, and could be used as promising photocatalyst for hydrogen production application.