Controllable Engineering of Surface Defects on ZnIn₂S₄ Nanosheets: Implications to Efficient Hydrogen Evolution Activity under Visible Light

Surface defect engineering is an effective approach for manipulating the electronic structure for enhancing photocatalytic hydrogen evolution reaction (HER) activities. The surface electronic structure of ZnIn 2 S 4 (ZIS) nanosheets was modified by introducing and regulating surface sulfur vacancies (S V ) through Ar-plasma treatment in this work. Optimized ZIS photocatalysts with surface S V deliver a high HER rate of 261.9 μmol·h –1 under visible light (λ > 420 nm), approximately 2.06-fold higher than that of the original ZIS. Significantly, the AQE value reaches 51.2% under 420 nm monochromic light irradiation. A series of characterization analyses prove that S V only exists on the ZIS surface. Furthermore, H 2 O-FTIR demonstrated that surface S V is more conducive to the adsorption of H 2 O molecules. Additionally, density functional theory calculations clarify the disparity in the kinetic process of H 2 evolution under the alkaline state over ZIS with/without S V . Therefore, Ar-plasma treatment is a beneficial method for regulating the surface S V on ZIS nanosheets, improving the efficiency of the photocatalytic HER.