Synergetic defect and local structure engineering to boost photocatalytic activity of ZnIn_2−xCu_xS₄nanosheets for H₂O₂production

Photocatalytic generation of H₂O₂ has attracted considerable attention because of its environmental benignity and economic merit. However, for the commercialization of photocatalytic H₂O₂ production, it is necessary to improve the activity and selectivity of noble-metal-free photocatalysts for the reduction of O₂ to H₂O₂. In this study, we developed a synergetic defect and local structure engineering approach to enhance the photocatalytic performance of transition-metal sulfides toward H₂O₂ production via simultaneous Cu substitution and exfoliation of ZnIn₂S₄. Combined Cu substitution and exfoliation allowed the introduction of considerable S vacancies and regulated the local structural distortion and electronic configuration. The Cu-substituted ZnIn_2−xCu_xS₄ nanosheets exhibited significantly enhanced photocatalytic activity for hydrogen peroxide production compared to pristine ZnIn₂S₄ and Ni-substituted ZnIn_2−xNi_xS₄ nanosheets. The high efficacy of Cu substitution–exfoliation in optimizing the photocatalytic activity was ascribed to the increase in S vacancies, enhancement of tetragonal distortion around the Cu substituent, and regulation of the electronic structure, which enhanced O₂ adsorption, increased visible-light absorptivity, prevented charge recombination, and improved the charge transfer and H₂O₂ production kinetics. This defect and local structure engineering strategy provides an effective means of developing highly efficient metal chalcogenide photocatalysts.