Vacancy-defect semiconductor quantum dots induced an S-scheme charge transfer pathway in 0D/2D structures under visible-light irradiation

Designing heterojunctions with a feasible charge transfer pathway is a promising strategy for establishing highly efficient artificial photosystems. The step-scheme (S-scheme) heterojunction has shown considerable potential in enhancing redox ability and charge transfer of photocatalysts. Herein, a hierarchical heterojunction involving vacancy-defect TiO2 quantum dots (QDs) and 2D g-C3N4 nanosheets was constructed using a multi-step assembly strategy. Computational and experimental studies show that the vacancy-defect TiO2 QDs can induce an S-scheme charge transfer pathway in the 0D/2D heterojunction under visible-light irradiation, which greatly improved the redox ability of charge carriers, enhanced the charge transfer and separation at interfaces, and facilitated the H2O adsorption and dissociation. This results in over 10-fold increase in hydrogen evolution reaction (HER) of photocatalytic water splitting for a wide range of carbon nitrides. The values achieved compare favorably with the best carbon nitride photocatalysts developed to date.