Efficient visible-light-driven hydrogen production with Ag-doped flower-like ZnIn₂S₄ microspheres

The zinc indium sulfide (ZnIn₂S₄) semiconductors have garnered significant interest in photocatalysis due to their environmentally friendly characteristics, appropriate bandgap, and high absorption coefficient. However, the exploration of advanced strategies to realize the effective and tailored doping still poses significant challenges in enhancing hydrogen evolution performance. In this work, a mild cation exchange strategy is reported to incorporate Ag cations into flower-like ZnIn₂S₄ microspheres, enabling the selective replacement of Zn atoms by Ag. Remarkably, the as-fabricated Ag-ZnIn₂S₄ exhibited exceptional photocatalytic hydrogen production performance, achieving a rate of 8098 μmol·g⁻¹· h⁻¹ under visible light irradiation. This is 4 times than that of pristine ZnIn₂S₄ (2002 μmol·g⁻¹· h⁻¹), and stands as the highest one among metal-doped-ZnIn₂S₄ photocatalysts ever reported. Along with the theoretical calculations, it has been confirmed that the enhanced photocatalytic hydrogen generation behavior can primarily be attributed to the synergistic effect with improved light absorption, reduced adsorption energy, increased active sites and optimized charge carrier transfer, induced by the cation exchange with Ag in ZnIn₂S₄. This work might provide some valuable insights on the design and development of highly efficient visible light driven photocatalysts for water splitting applications.