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In this paper, NiCo2S4 was coated on the surface of WS2 of a 1T/2H mixed phase by a two-step hydrothermal method to form an in situ core–shell structure. The unique S-scheme heterojunction of the NiCo2S4@WS2 core–shell composite photocatalyst improved the easy recombination of carriers caused by the narrow band gap of NiCo2S4 and WS2, and improved the photocatalytic hydrogen production performance. The loading ratio of NiCo2S4@WS2, the addition of Eosin Y, and the pH value of TEOA were optimized. Under the optimal conditions, the hydrogen production rate reached 5.814 mmol g−1 h−1, which is about 8.55 times and 3.35 times the hydrogen evolution rates of NiCo2S4 and WS2, respectively. The composite catalyst exhibits excellent charge separation efficiency in photoelectrochemistry, PL and BET tests, carrier transport rate and large specific surface area that can provide more active sites, which are the main factors for the improvement of the hydrogen evolution performance. This paper demonstrates new design strategies to drive efficient photocatalytic hydrogen production by building in situ core–shell structures and optimizing the carrier transport paths, which will yield new insights. [ABSTRACT FROM AUTHOR]

The development of high-performance and highly stable electrocatalysts is crucial and challenging for the hydrogen evolution reaction (HER). MOFs complexed with SnS2 can form complexes with inserted structures, and their large specific surface area and numerous pores favor mass transfer, exposing the S active sites to more SnS2, improving the utilisation of the active sites and enhancing the catalytic activity for the HER. Structural collapse can be hindered to improve the stability of the HER composites. Herein, six different kinds of SnS2 were synthesized by a hydrothermal method under discrete conditions, and SI8-SnS2 was screened out to have optimal morphology and electrocatalytic performance. Two innovative SnS2@Ni-MOF and SnS2@HKUST-1 as efficient electrocatalysts were synthesized by a facile grinding method for hydrogen generation. SnS2@Ni-MOF and SnS2@HKUST-1 catalysts showed lower overpotentials of 117 mV and 142 mV at 10 mA cm−2 (η10) and smaller Tafel slopes (58 mV dec−1 and 93 mV dec−1) than six different kinds of SnS2, Ni-MOF and HKUST-1 in 0.5 M H2SO4. Meanwhile, the Cdl values for SnS2@Ni-MOF and SnS2@HKUST-1 were estimated to be 11.5 mF cm−2 and 8.0 mF cm−2, and the stabilities of SnS2, Ni-MOF, HKUST-1, SnS2@Ni-MOF, and SnS2@HKUST-1 were tested at a current density of 10 mA cm−2. The current densities of SnS2@Ni-MOF and SnS2@HKUST-1 were stable over 8 h compared to the pure samples, and SEM, XPS tests were run after the HER test, indicating that the materials have excellent electrocatalytic stability. The syntheses of SnS2@Ni-MOF and SnS2@HKUST-1 enhance their intrinsic catalytic activity, and the porous structure promotes mass transfer efficiency, thereby improving the HER performance, which will guide the development of new and promising electrocatalysts for HER. [ABSTRACT FROM AUTHOR]

Metal halide perovskites, such as iodine methylamine lead (MAPbI3), have received extensive attention in the field of photocatalytic decomposition of HI for hydrogen evolution, due to their excellent photoelectric properties. In this paper, a new MAPbI3-based composite, MoC/MAPbI3, was synthesized. The results show that 15 wt% MoC/MAPbI3 has the best hydrogen production performance (38.4 μmol h−1), which is approximately 24-times that of pure MAPbI3 (1.61 μmol h−1). With the extension of the catalytic time, the hydrogen production rate of MoC/MAPbI3 reached 165.3 μmol h−1 after 16 h due to the effective separation and transfer of charge carriers between MoC and MAPbI3, showing excellent hydrogen evolution rate performance under visible light. In addition, the cycling stability of MoC/MAPbI3 did not decrease in multiple 4 h cycle tests. This study used the non-precious metal promoter MoC to modify MAPbI3, and provides a new idea for the synthesis of efficient MAPbI3-based composite catalysts. [ABSTRACT FROM AUTHOR]

Piezocatalytic hydrogen evolution has emerged as a promising field for the collection and utilization of mechanical energy, as well as for generating sustainable energy throughout the day. Hexagonal CdS, an established semiconductor photocatalyst, has been widely investigated for its ability to split water into H2. However, its piezocatalytic performance has received less attention, and the relationship between its structure and piezocatalytic activity remains unclear. In this study, we prepared 3D ultrathin CdS nanoflowers with high voltage electrical response and low impedance. In pure water, without the use of any cocatalyst, CdS exhibited a piezoelectric catalytic hydrogen production rate of 1.46 mmol h−1 g−1, which was three times higher than that of CdS nanospheres (0.46 mmol h−1 g−1). Furthermore, the value-added oxidation product H2O2 was produced during the process of piezoelectric catalysis. These findings provide new insights for the design of high-efficiency piezoelectric catalytic hydrogen production. [ABSTRACT FROM AUTHOR]

As a research hotspot, 2D-MoS2 has been regarded as a low-cost substitute for platinum, and has fascinated researchers worldwide. Two crystalline phases of MoS2, i.e. the metallic octahedral 1T phase and semiconducting trigonal prismatic 2H phase, have been extensively analysed. In comparison to 2H-MoS2, the 1T phase exhibits enhanced and unique physicochemical properties. Designing a structure with two-dimensional mixed-phase MoS2, i.e. 1T/2H-MoS2 nanosheets, via phase engineering for effective charge separation and migration has received growing interest in the field of photocatalytic hydrogen generation. In this study, by varying the wt% of ammonium bicarbonate via a facile hydrothermal technique, a series of 1T/2H-MoS2 nanosheets have been fabricated. The presence of the corresponding elements, the electronic environment, phase purity, morphology and phase distinction were confirmed by Raman, XPS, XRD and HRTEM analyses. Additionally, the impedance data and the photocurrent density of the photocatalysts verify the efficient charge separation and transfer phenomenon. In accordance with the electrochemical measurements, the developed mixed-phase MoS2 nanosheets exhibit a six times greater current density than 2H-MoS2. Furthermore, the highest response of photocatalytic hydrogen production is observed with the photocatalyst with 79% 1T phase, which is about 17 times greater than that of pristine 2H-MoS2 due to the enrichment of active sites on both the edges and basal plane as well as the enhanced electronic conductivity due to the 1T phase. This study indicates that with the construction of a heterophase, i.e. 1T/2H-MoS2 nanosheets, the photocatalytic hydrogen evolution capability can be boosted, providing new insights regarding these materials. [ABSTRACT FROM AUTHOR]

A dual-phase transition metal nitride (TMN) based Co4N- WNx system has been fabricated using nitridation of CoWO4. The interface between centrosymmetric Co4N and non-centrosymmetric WNx promotes charge carrier separation. This system also shows piezoelectric behavior. The piezoelectric property has been proved using piezoelectric force microscopy (PFM) measurements. In addition, modulating the noncentrosymmetric structure of Co4N- WNx allows a hydrogen production rate of about 262.7 μmol g-1 h-1 in pure water. We also show that the piezocatalytic hydrogen evolution efficiency is satisfactory. Co4N- WNx can also help achieve simultaneous piezocatalytic hydrogen production and RhB degradation. This work provides a novel strategy for designing efficient piezocatalytic materials. [ABSTRACT FROM AUTHOR]

Recently, much attention has been focused on the development of photocatalysts for hydrogen evolution. Up to now, efficient hydrogen generation is still greatly challenging due to the restraints of the surface redox reaction rate, and the introduction of a co-catalyst is one of the keys to this problem. Here, dual non-noble co-catalysts NixP and Mn3O4 were proposed and prepared on a g-C3N4/red phosphorus (CNP) hybrid structure with a high light adsorption capability by a two-step photo-deposition method. The photo-excited charge on the composite catalyst separate and transfer from C3N4 to red phosphorous due to a type I heterojunction structure. NixP and Mn3O4 act as reductive and oxidative co-catalysts, respectively. The hydrogen production rate was 5851.3 μmol g−1 h−1, 12.4 times that of pure CNP. The consistent catalytic activity in an actual 25 mL flask for hydrogen evolution over eight hours accumulated 245.08 μmol H2 under solar simulated irradiation. This work provides practical reference for the development of a novel inexpensive photocatalyst system. [ABSTRACT FROM AUTHOR]

Herein we have demonstrated the synthesis of nitrogen vacancy enriched exfoliated B-doped g-C3N4 (e-BCN) through a facile thermal exfoliation method, characterized it using different analytical techniques and compared its photocatalytic activity with that of bulk B-doped g-C3N4 (BCN). The decrease in peak intensity and slight shift of the 2 value in the PXRD patterns confirmed the successful exfoliation of bulk BCN to an e-BCN nanosheet. FESEM and HRTEM images also indicated the formation of a thin layered nanosheet of e-BCN as compared to bulk BCN. The PL and EIS data suggested the reduced recombination rate and superior separation capability of the photo-generated charge carriers of e-BCN. The introduction of nitrogen vacancies on the surface of e-BCN is confirmed by the FTIR and XPS analyses. The increased photocurrent density of 524 μA cm−2 displayed by e-BCN indicated the better availability of photo-generated electrons due to the higher separation of charge carriers than in the bulk BCN. The as-prepared e-BCN nanosheet exhibited enhanced photocatalytic performance 1.2 and 3.7 fold greater than that of bulk BCN towards ciprofloxacin degradation and H2 generation, respectively, under visible light irradiation. The excellent photocatalytic behavior of e-BCN was ascribed to the augmented active sites with reduced recombination efficiency and increased separation ability of the photo-induced e−/h+ pairs of the e-BCN nanosheet. This work suggested the facile fabrication of e-BCN through the thermal exfoliation process and its photocatalytic activity towards pollutant degradation and hydrogen evolution. [ABSTRACT FROM AUTHOR]

Promoting electron–hole separation and migration is one of the important factors affecting the rate of photocatalytic hydrogen production. Herein, we first prepared NixCo1−xP modified ZnIn2S4 (ZIS) nanoflowers via a low-temperature solvothermal method. Among these catalysts, 2%Ni0.1Co0.9P–ZIS exhibited the highest photocatalyst hydrogen production rate of 3839 μmol g−1 h−1 under visible light irradiation (λ > 420 nm), which is 5.4 times and 2.4 times higher than that of pure ZIS (714 μmol g−1 h−1) and 2%Pt–ZIS (1651 μmol g−1 h−1), respectively. The enhancement is due to the formation of close contact between ZIS and Ni0.1Co0.9P, which can promote electron–hole separation and migration. Moreover, the hydrogen production rate of Ni0.1Co0.9P–ZIS is much higher than that of Ni2P–ZIS and CoP–ZIS, which is attributed to the synergistic effects of metallic elements. After five photocatalytic cycles, the photocatalytic activity has no obvious change, suggesting excellent chemical stability. This study may provide new ideas for the formation of noble metal-free metal phosphide loading ZIS for photocatalytic hydrogen evolution. [ABSTRACT FROM AUTHOR]

Photochemical water splitting offers an economic and sustainable approach for solar energy conversion into hydrogen fuel to mitigate the problem of greenhouse gas emissions. To this end, exploring novel semiconductor photocatalysts, which have efficient light absorption and thermodynamically favorable band alignment for water splitting, is crucial. Here, we rationally develop a new photocatalyst of CuInP2S6 nanosheets to generate hydrogen gas under light illumination. The CuInP2S6 nanosheet (with a thickness of around 4–7 nm) photocatalyst exhibits a high hydrogen production rate of 804 μmol g−1 h−1, eight times higher than that of the microsheet counterpart, due to the introduced abundant sulfur vacancies. Experimental characterization and theoretical calculations verify that the prolonged carrier lifetime and optimized band alignment in ultrathin CuInP2S6 nanosheets boost photocatalytic hydrogen evolution. This work opens a new avenue for photocatalysis via using novel layered binary metal phosphorous trichalcogenides. [ABSTRACT FROM AUTHOR]

Typical non-metallic semiconductor carbon nitride (CN) has enormous potential in the field of photocatalysis, but the easy recombination of the photo-generated charges severely limits its practical applications. Herein, oxygen-doped and nitrogen vacancy co-modified carbon nitride (ODCN) was prepared by simple reduction and oxidation treatments. The experimental results show that the modified CN can effectively enhance the photocatalytic activity, indicating that there is a synergy between oxygen doping and nitrogen vacancy. The photocatalytic hydrogen generation rate of ODCN is 364 μmol g−1 h−1, which is higher than that of bulk CN, nitrogen vacancy-modified carbon nitride (DCN) and oxygen-doped modified carbon nitride (OCN). As a consequence, our work provides a neoteric idea for the co-modification of carbon nitride by a variety of methods, which can significantly improve the photocatalytic activity of carbon nitride and is expected to be applied in practical applications. [ABSTRACT FROM AUTHOR]

The rapid separation and transport of photogenerated carriers are pivotal toward enhancing the photocatalytic performance. Herein, CdS nanoparticles are grown in situ on oxygen deficiency-rich WO3−x nanosheets, successfully providing a direct Z-scheme CdS/WO3−x heterojunction to enhance photocatalytic hydrogen production. We demonstrate an effective electron collection in the Z-scheme CdS/WO3−x heterojunction by regulating the relative content of WO3−x. The optimized CdS/20 wt% WO3−x (CW20) affords a high photocatalytic hydrogen production rate of 6545.3 μmol g−1 h−1 in lactic acid aqueous solution under visible light (400–800 nm), which is about 54.1 times that of pure CdS (121.0 μmol g−1 h−1). In addition, CW20 also provides a considerable external quantum efficiency (EQE) of 10.03% at λ = 420 nm. The best-performing CW20 sample is explored by cyclic stability experiment and XRD characterization after hydrogen production, which reveals the robust stability of CW20. The excellent photocatalytic activity can be attributed to the formation of a Z-scheme CdS/WO3−x heterojunction, resulting in an efficient spatial separation of photogenerated carriers. Electron and hole catalytic centers are maintained in two separate components to minimize the adverse products of photocatalytic hydrogen production. This study uncovers the role of oxygen deficiency based on the Z-scheme heterojunction in affecting electron transfer and reaction sites, opening new opportunities for achieving efficient hydrogen production. [ABSTRACT FROM AUTHOR]

A facile synthetic route, by using rhombic dodecahedral zeolitic imidazolate framework-8 (ZIF-8) as the structure template, is devoted to fabricating the ZnS/ZnIn2S4 hybrid heterojunction; the compact heterostructure was produced by combining the sulfurization of ZIF-8 and the in situ precipitation of ZnIn2S4 in one pot. The resulting ZnS nanoparticles of about 100 nm were uniformly dispersed in the folds of flower-like ZnIn2S4, whose structure is beneficial for charge transfer at the heterointerface. The additional quantities of ZIF-8 are varied to find an optimum ratio of the two components to obtain the best photocatalytic activity. In the photocatalytic hydrogen generation irradiated by simulated solar light, all the ZnS/ZnIn2S4 hybrid photocatalysts displayed improved hydrogen production rates compared to single ZnS or ZnIn2S4, and the best hydrogen production rate of 453.4 μmol h−1 g−1 is obtained by ZnS/ZIS-20, whose value is approximately 4 times higher than that of single ZnIn2S4. The electrochemical properties of the ZnS/ZnIn2S4 hybrid photocatalysts were measured to explore the charge transfer mode at the interface, and the band structure and enhanced photocatalytic hydrogen generation mechanism have been proposed. The excellent recycling properties of hydrogen production indicated the prospective applications of this kind of ZIF-derived metal sulfide in photocatalytic reactions. [ABSTRACT FROM AUTHOR]

Efficient and cost-effective photocatalysts are pivotal for advancing large-scale solar hydrogen generation. Herein, we report a composite photocatalyst by incorporating MoS2 quantum dots (MoS2 QDs) as a cocatalyst into Cs3Bi2I9, resulting in a high enhancement in photocatalytic performance. Remarkably, the optimum MoS2 QDs/Cs3Bi2I9 composite achieves an impressive hydrogen evolution rate (6.09 mmol h−1 g−1) in an ethanol and HI/H3PO2 mixed solution. This rate is 8.8 times higher than pristine Cs3Bi2I9 (0.69 mmol h−1 g−1) and notably surpasses Pt/Cs3Bi2I9 (2.47 mmol h−1 g−1). Moreover, the composite displays exceptional stability during an 18-hour reaction, showcasing its potential for sustainable photocatalytic hydrogen evolution. [ABSTRACT FROM AUTHOR]

Motivated by the recent report of a heteroleptic ruthenium bis-terpyridine complex [Ru(toltpy)(bipytpy)](PF6)2 (toltpy: 4′-(tolyl)-2,2′:6′,2′′-terpyridine; bipytpy: 4′-(4-bromophenyl)-4,4′′′:4′′,4′′′′-di-pyridinyl-2,2′:6′,2′′-terpyridine) capable of driving the photo-evolution of hydrogen with a constant rate of activity for 12 days [M. Rupp et al., Inorg. Chem., 2019, 58, 9127–9134], we investigated the impact of an internal electron donor on the photoactivity of three new ruthenium bis-terpyridine photosensitizers. We used 4′-(N,N-dimethylaminophenyl)-4,4′′-di-tert-butyl-2,2′:6′,2′′-terpyridine (Dtpy) as the donor ligand. These complexes also bear peripheral coordination sites at various positions on the terpyridine backbone, allowing for photosensitizer–catalyst interactions. Their performances in photocatalysis under blue and green light (450 and 525 nm, respectively) were measured, in the presence of triethanolamine, using a cobaloxime catalyst [Co(dmgH)2(H2O)2](BF4)2. Complexes C1[Ru(Dtpy)(pytpy)](PF6)2 (pytpy: 4′-(pyridin-4-yl)-2,2′:6′,2′′-terpyridine) and C3[Ru(Dtpy)(bipytpy)](PF6)2 appeared to have a photostability similar to that of [Ru(toltpy)(bipytpy)](PF6)2 but with lower activity rates, while C2[Ru(Dtpy)(pz2bpy)](PF6)2 (pz2bpy: 2,6-di(pyrazin-2-yl)-4,4′-bipyridine) showed a better peak activity, however, followed by a progressive decay. After 24 hours, complexes C1, C2 and C3 had reached TONs of 18, 35 and 52 under blue light and 14, 20 and 47 under green light, respectively, and were still found to be active. Their photophysical and electronic properties are discussed to rationalize the photocatalytic trends. [ABSTRACT FROM AUTHOR]

In terms of energy acquisition, research on the photocatalytic cracking of water to produce hydrogen has become a hub for us to make a transition from theoretical research to practical applications. Charge separations and surface redox reactions of semiconductors are key factors that affect hydrogen production activity. In this study, we used an n-type semiconductor WP as a cocatalyst to modify the solid solution of ZnxCd1−xS and found it to have excellent photocatalytic activity under visible light irradiation. Ultraviolet diffuse reflectance spectroscopy showed the red shift of the absorption band of the composite catalyst and the strong absorption of visible light. Under the action of the matching energy band structure, the fluorescence lifetime of the composite catalyst is shortened (2.33 ns) and the electron injection rate is accelerated (Ket = 0.58 × 109 s−1). Under these favorable conditions, the increased hydrogen production activity of the composite catalyst is finally reflected in the enhanced hydrogen production rate, which reached up to 15 028.6 μmol g−1 h−1. In addition, the yield of hydrogen produced by adding a fresh lactic acid catalyst in the fifth cycle after four cycles of testing was greatly improved. Obviously, the addition of WP turns the composite catalyst into a photocatalyst with high efficiency, stability and is a non-noble metal cocatalyst. Finally, through a series of characterization experiments (SEM, TEM, XPS, BET, Mott–Schottky et al.), we proposed the possible mechanism of WP/ZnxCd1−xS that efficiently promotes hydrogen production. This provides new understanding for designing an effective cocatalyst modified semiconductor to improve photocatalytic activity. [ABSTRACT FROM AUTHOR]

The separation and transfer of photoelectrons is a crucial factor in the process of photocatalysis. Herein, we successfully designed and prepared WP as a cocatalyst, modified the g-C3N4(CN)/CdS heterojunction structure, achieved the effective separation and directional transfer of photoelectrons, and also efficient photocatalytic hydrogen evolution. In addition, the as-prepared WP–CN/CdS composite photocatalyst not only prominently improved the separation and pre-assigned transfer of photogenerated electrons, but also had abundant surface active sites, which greatly improved the photocatalytic performance of the catalyst; namely, the highest photocatalytic activity of WP–CN/CdS was achieved at 5% WP content and the highest hydrogen production rate could reach 18 238.89 μmol h−1 g−1, which is about 12.49 times that of pure CdS. The detailed characterization studies with SEM, TEM, XRD, XPS, DRS, UV–vis, BET, transient photocurrent, FT-IR etc. effectively supported the abovementioned results, and all the characterization results were in good agreement with each other. Moreover, a possible mechanism of the photocatalytic reaction in the WP–CN/CdS system is proposed. [ABSTRACT FROM AUTHOR]