Synergistic effect of oxygen defect and doping engineering on S-scheme O-ZnIn2S4/TiO2-x heterojunction for effective photocatalytic hydrogen production by water reduction coupled with oxidative dehydrogenation

Aiming to the unwanted photocatalytic hydrogen production systems using sacrifice agents, a well-design S-scheme O-ZnIn2S4/TiO2-x heterojunction was fabricated to realize photocatalytic hydrogen production via water reduction coupled with organic oxidative dehydrogenation. As supported by DFT calculations and experimental analysis, owing to the synergistic effect of oxygen defect and doping engineering, a tailored energy band structure alignment with higher redox potentials and larger Fermi level potential difference are achieved, resulting in more efficient S-scheme interface charge transfer and separation efficiency, thus improving the photocatalytic activity of O-ZnIn2S4/TiO2-x. The optimal O-ZnIn2S4/TiO2-x photocatalyst shows remarkable H2 and benzaldehyde production rate of 2584.9 μmol g-1h−1 and 2880.5 μmol g-1h−1 under visible light, which are 52.5 and 66.4 times as high as those over blank TiO2. Interestingly, this coupled reaction system also displays superior H2 evolution activity compared to sacrificial reagent systems of Na2SO3/Na2S and triethanolamine. Further quenching and EPR experiments reveal that both water and organic molecules provide protons for H2 production.