Unveiling Charge Transfer in a Ni-Doped ZnO/Zn _0.25 Cd _0.75 S Z-Scheme Heterojunction for Enhanced Photocatalytic H ₂ Evolution

ZnO-based photocatalysts severely limit solar energy utilization efficiency due to their exclusive CO₂absorption of ultraviolet light. In this study, Ni-ZnO/Zn_0.25Cd_0.75S Z-scheme heterojunctions were constructed to enhance photocatalytic performance. Results demonstrate that Ni²⁺ doping not only broadens the light absorption range of ZnO but also introduces oxygen vacancies that effectively suppress carrier recombination. Meanwhile, heterojunction construction facilitates the uneven adherence of Zn_0.25Cd_0.75S particles to rod-shaped ZnO. A Z-type charge transfer mechanism has been constructed under the influence of the built-in potential at the interface. This mechanism maintains strong redox capacity and achieves efficient carrier separation, improving the hydrogen evolution activity of the composite photocatalyst. The hydrogen production rate reaches 16.5 mmol·g^-1·h^-1, which is 56 and 9.9 times that of Ni-ZnO and Zn_0.25Cd_0.75S, respectively.