Synergistic Effect of the Surface Vacancy Defects for Promoting Photocatalytic Stability and Activity of ZnS Nanoparticles

High activity, high stability, and low cost have always been the pursuit of photocatalyst design and development. Herein, a simple method is used to integrate abundant anion vacancies (VS) and cation vacancies (VZn) on the surface of ZnS (M–ZnS), deriving VS and VZn pairs (vacancy pairs), isolated Zn atoms (Zniso), and isolated S atoms (Siso). Abundant surface vacancy defects fully expose and activate the surface atoms, regulate the band structure, and significantly improve the separation of photogenerated carriers. M–ZnS is endowed with high activity, and the average hydrogen production rate of the optimal sample increases to 576.07 μmol·g–1·h–1 (λ > 400 nm). Theoretical simulations indicate that the activated Zn atoms are the dominant active sites via the formation of a Zn–OH bond with H2O. Especially, the strong interactions of electrons in atomic orbitals at vacancy pairs and the introduction of VZn are conducive to high stability. The optimal sample maintains an average hydrogen production rate of 6.59 mmol·g–1·h–1 (300 W Xe lamp) after nine cycles. Hence, this work deepens the understanding of vacancy defects and provides an idea for the design of a stable photocatalyst.