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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]

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]

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]