A Z-scheme ZnIn₂S₄/ZnS heterojunction catalyst: insight into enhanced photocatalytic performance and mechanism

The reasonable design of a highly efficient photocatalyst to improve its hydrogen production performance has attracted extensive attention. In this work, ZnIn2S4/ZnS (ZIS/ZnS) heterojunctions were constructed through a one-step solvothermal method, which ensures a good microscopic relationship between different phases and keeps their interfaces in close contact. The optimized ZIS/ZnS catalyst exhibited exceptionally enhanced photocatalytic activity under simulated AM 1.5G irradiation, and the maximum hydrogen evolution rate reached 464.1 mu mol h(-1), which was 16.2 and 7.3 times higher than that of pure ZnS and ZIS, respectively. Photo/electrochemical analyses proved that the ZIS/ZnS heterojunction has high charge separation efficiency and a strong redox ability. A Z-scheme electron transfer mechanism was proposed to explain the dramatic increase in photocatalytic activity which was based on photodeposition experiments. In addition, the catalyst also showed excellent hydrogen evolution activity under visible light irradiation (lambda > 420 nm). We explored the charge transfer mechanism in detail under different light conditions, employing in situ XPS and photo-deposition experiments.