Cu-Doped ZnIn2S4 with Sulfur Vacancy Expedites Carrier Separation for Efficient Photocatalytic Hydrogen Evolution

Synchronously enhancing the light response range and electron–hole separation efficiency is essential to improve photocatalytic activity. Herein, we synthesized a Cu-doped ZnIn2S4 (ZIS) catalyst with S-vacancy (Cun-VZIS) via hydrothermal synthesis, incorporating sulfur vacancies and directionally substituting copper ions for zinc ions. The experimental results elucidate the synergistically photocatalytic mechanism associated with the two types of defects. Both the sulfur vacancies within the structure and the copper doping sites lead to a reduction in the size of the ZnIn2S4 unit cell. The sulfur vacancy traps electrons, thereby mitigating the recombination of photogenerated carriers. Meanwhile, the copper ions optimize the carrier migration pathways, enhancing the overall carrier separation efficiency. Consequently, Cu1.5-VZIS demonstrates a stable and markedly enhanced photocatalytic hydrogen production activity, achieving a performance that is 7.5 times greater than that of pristine ZIS. Our study elucidates the effect of vacancy defects and ion doping on the photogenerated charge dynamics in ZIS, and paves a novel pathway for optimizing carrier dynamics through the concurrent utilization of both types of defects.