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ZnIn2S4 (ZIS) is an efficient photocatalyst for solar hydrogen (H2) generation from water splitting owing to its suitable band gap, excellent photocatalytic behaviour and high stability. Nevertheless, modifications are still necessary to further enhance the photocatalytic performance of ZIS for practical applications. This has led to our interest in exploring phosphorus doping on ZIS for photocatalytic water splitting, which has not been studied till date. Herein, phosphorus-doped ZnIn2S4 (P-ZIS) was modelled via Density Functional Theory to investigate the effects of doping phosphorus on the structural and electronics properties of ZIS as well as its performance toward photocatalytic water splitting. This work revealed that the replacement of S3 atom by substitutional phosphorus gave rise to the most stable P-ZIS structure. In addition, P-ZIS was observed to experience a reduction in band gap energy, an upshift of valence band maximum (VBM), an increase in electron density near VBM and a reduction of H* adsorption–desorption barrier, all of which are essential for the enhancement of the hydrogen evolution reaction. In overall, detailed theoretical analysis carried out in this work could provide critical insights towards the development of P-ZIS-based photocatalysts for efficient H2 generation via solar water splitting. [ABSTRACT FROM AUTHOR]

Over the years, researchers have placed increasing focus on extending the application of photocatalytic hydrogen (H2) evolution to seawater. Herein, a photocatalytic system with a unique combination of P‐doped Zn0.5Cd0.5S (pZCS) and noble‐metal‐free CoP is first fabricated to evaluate the synergy between them. The resultant sample achieves a significantly boosted photocatalytic H2 evolution reaction (HER) with a rate of 5488.8 μmol g−1 h−1, which is an almost 50‐fold enhancement from its pristine ZCS counterpart. Impressively, the CoP–pZCS composite also demonstrates overall water splitting where no sacrificial reagent is used, with an H2 evolution rate of 154.6 μmol g−1 h−1. The sample is then tested for its HER activity in seawater, and 3956.0 μmol g−1 h−1 of H2 is acquired. The main factor that contributes to its high performance in seawater despite various distractions coming from the abundance of ions present is the synergistic relation between pZCS and CoP. The midgap state procured through the introduction of the P dopant has excellent electron–hole separating ability, and CoP further serves as an electron sink where the photogenerated electrons can rapidly assemble. Ultimately, the charge carrier recombination within the resultant composite is greatly hindered, thus a spectacular photocatalytic HER in seawater is enabled. [ABSTRACT FROM AUTHOR]

Molybdenum disulfide quantum dots (MoS 2 QDs) decorated bismuth sulfide (Bi 2 S 3 ) photocatalyst was synthesized. Photoluminescence characterization showed that the as-developed MoS 2 QDs possessed intriguing up-conversion and down-conversion properties, indicating their capability to harness energy from the light spectrum ranging from ultraviolet (UV) to near-infrared (NIR). In this study, the highest hydrogen yield of 17.7 mmol/g.h was achieved by 0.14MoS 2 QD/Bi 2 S 3 , which was almost 4.5 folds higher than that of undoped Bi 2 S 3 under stimulated solar light irradiation. Furthermore, examination of the 0.14MoS 2 QD/Bi 2 S 3 photocatalysts under NIR irradiation showed a significant photocurrent response and an accumulative H 2 yield of 53.6 μmol/g after 6 h reaction. This is a major breakthrough as most photocatalysts can only be activated under UV and/or visible light irradiation. This work provides new insights into the design of MoS 2 QD/Bi 2 S 3 for harnessing energy from a broad solar spectrum to photocatalytically split water to produce hydrogen. [ABSTRACT FROM AUTHOR]

In this contribution, the effectiveness of tailor-made multi-walled carbon nanotubes (MWCNTs) as a solid-state electron mediator for facilitating Z-schematic water splitting is demonstrated. An anisotropic Zn 0.5 Cd 0.5 S-MWCNT-TiO 2 ternary core-shell nanocomposites fabricated by a facile coating and hydrothermal route renders a much higher photocatalytic activity than the corresponding single- and two-component systems, revealing MWCNTs can shuttle photogenerated electrons from PS II (TiO 2 ) to PS I (Zn 0.5 Cd 0.5 S). This unique type of vectorial electron transfer between the two photosystems imparts an efficient spatial charge isolation and endows suitable relative band positions with strong redox ability to the Z-scheme system. Consequently, the simulated solar-light-driven (AM 1.5) photocatalytic H 2 evolution rate of the as-prepared Zn 0.5 Cd 0.5 S-MWCNT-TiO 2 photocatalyst (21.9 μmol h −1 ) is ca. 4.5- and 2.8-fold enhancement over pristine Zn 0.5 Cd 0.5 S and MWCNT-Zn 0.5 Cd 0.5 S samples, respectively. The structural and chemical properties of the typical photocatalysts were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and ultraviolet–visible diffuse spectroscopy (UV–Vis). Besides, electrochemical characterizations (transient photocurrent, Nyquist and Mott-Schottky measurements) were performed to depict the ascendency of the Z-scheme system. Based on the outcomes of the experiment, a plausible charge transfer mechanism for the Z-schematic Zn 0.5 Cd 0.5 S-MWCNT-TiO 2 system was postulated. [ABSTRACT FROM AUTHOR]

• Breaking of intermolecular bonding enhanced photocatalytic performance of GCN. • Defects in crystallinity induced mid-gap states. • Existence of a mid-gap state in ACN supplied a secondary H+/H 2 reduction site. • The optimum ACN sample displayed activity 2-fold higher than that of pristine GCN. In this work, the intramolecular structure of a pristine graphitic carbon nitride (GCN) was modified to investigate how it would affect the photocatalytic activity towards hydrogen evolution reaction (HER) under simulated solar irradiation. The intramolecular bonding of GCN was broken by subjecting it to a simple thermal treatment under a controlled environment. Both experimental and computational studies revealed that removal of inter-heptazine CN(H)C groups from the pristine structure induced an amorphous phase and additional energy bands to GCN. It was also observed that a mid-gap state was formed between the conduction band (CB) of the amorphous carbon nitride (ACN) and the H+/H 2 reduction potential. The presence of the mid-gap state not only served as an additional reduction site for HER, but also acted as a buffer to reduce the recombination rate of photogenerated charge carriers. The optimum ACN sample displayed an enhanced photocatalytic performance achieving a HER rate of 789 µmol/g cat , which was about 2-fold higher than that of pristine GCN. This could be ascribed to the synergistic effect of improved light absorption, increased surface area, suppressed charge recombination and increased charge carrier densities for the ACN samples to drive the overall reduction–oxidation process. [ABSTRACT FROM AUTHOR]