Effect of surface defect states on Zn(1−x)CdxS for enhanced photocatalytic hydrogen evolution

Photocatalytic H2 production using solar energy has received great attention, but suffers from low photocatalytic efficiency. Herein, Zn(1−x)CdxS solid solution with different Zn/Cd molar ratio was synthesized by a solvothermal method, and tested for photocatalytic H2 production from water. The bandgap, charge carrier separation efficiency and surface defect states of the Zn(1−x)CdxS can be adjusted by altering the Zn/Cd molar ratio. The separation efficiency of photogenerated electrons and holes was greatly enhanced with the Zn/Cd molar ratio of 0.8:0.2. Moreover, the Zn0.8Cd0.2S exposed most surface defect states compared to those of other Zn(1−x)CdxS, which can be act as electron pools and active sites for improving photocatalytic H2 production. Therefore, when the molar ratio of Zn/Cd is 0.8:0.2, the Zn0.8Cd0.2S exhibited the best performance for photocatalytic H2 production with the H2 production rate of 7.71 mmol·g-1·h-1, which is much higher than that of ZnS (17 μmol·g-1·h-1) and CdS (5.37 μmol·g-1·h-1). This work provides an in-depth understanding of the surface defect states for enhancing the photocatalytic H2 production.