Synergistic selenium doping and colloidal quantum dots decoration over ZnIn2S4 enabling high-efficiency photoelectrochemical hydrogen peroxide production

Photoelectrochemical (PEC) water splitting to value-added hydrogen peroxide (H2O2) production is more promising than the traditional O2 evolution. However, enabling efficient PEC H2O2 generation is still challenging due to competitive two-/four-electron water oxidation pathways. In this work, ZnIn2S4 (ZIS) photoanodes were engineered by Se doping and colloidal quantum dots (QDs) modification to boost the PEC H2O2 evolution efficiency. Morphology and elemental studies testify the successful Se doping in ZIS and the anchoring of QDs on ZIS-Se photoelectrodes. Photoinduced carrier kinetics investigation verifies the optimized band bending, suppressed charge recombination, and promoted charge transfer in as-prepared ZIS-Se and ZIS-Se/QDs photoanodes, exhibiting inhibited four-electron O2 evolution and facilitated two-electron H2O2 production during PEC water oxidation, as evidenced by the density functional theory (DFT) calculations. Accordingly, the Se-doped and QDs-decorated ZIS photoelectrodes demonstrate a gradually less upward band bending and improved photo-excited hole transfer to the surface, delivering a maximum H2O2 production rate of 1.32 μmol min−1 cm−2 with a Faraday efficiency of 86 % at 1.23 V versus reversible hydrogen electrode (RHE) under one sun illumination.