Synergetic defect and local structure engineering to boost photocatalytic activity of ZnIn2-xCuxS4 nanosheets for H2O2 production

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 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 hydrogen evolution reaction kinetics. This defect and local structure engineering strategy provides an effective means of developing highly efficient metal chalcogenide photocatalysts.