Dual sulfur defect engineering of Z-scheme heterojunction on Ag-CdS

Photocatalytic production of hydrogen peroxide (H2O2) using sunlight as an energy source, water and molecular oxygen as feedstock is considered as a green and sustainable promising strategy to solve the energy and environmental crisis. Despite significant improvements in photocatalyst design tuning, however, the relatively low photocatalytic H2O2 productivity is still far from satisfactory. Herein, we developed a multi-metal composite sulfide (Ag-CdS1-x@ZnIn2S4-x) with double S vacancies and hollow core-shell Z-type heterojunction structure for H2O2 generation by a simple hydrothermal method. The unique hollow structure improves the utilization of light source. The existence of Z-type heterojunction promotes the spatial separation of carriers, and the core-shell structure increases the interface area and active sites. Under visible light irradiation, Ag-CdS1-x@ZnIn2S4-x had a high hydrogen peroxide yield of 1183.7 μmol h-1 g-1, which was 6 times that of CdS. The electron transfer number (n = 1.53) obtained from the Koutecky-Levuch plot and DFT calculation confirm that the presence of dual disulfide vacancies provides good selectivity of 2e- O2 reduction to H2O2. This work provides new insights into the regulation of highly selective two-electron photocatalytic H2O2 production, and also provides new ideas for the design and development of highly active energy conversion photocatalysts.