Tungsten and oxygen dual vacancies regulation of the S-scheme ZnSe/ZnWO4 heterojunction with local polarization electric field for efficient CO2 photocatalytic reduction

Inefficient separation and sluggish transfer of photogenerated charges on the photocatalyst is one of the bottlenecks for CO 2 photocatalytic reduction. In this study, the ZnSe/ZnWO 4 heterojunction with tungsten vacancies and oxygen vacancies (ZZ-30%-Vw,o) was synthesized by hydrothermal process and post-etching method for CO 2 reduction. Various characterizations showed superior structural and optical properties of the ZZ-30%-Vw,o heterojunction; results of ESR and work function calculation demonstrated that the heterojunction conformed to S-scheme charge transfer mechanism. Results of various tests and density functional theory (DFT) calculation confirmed the existence of W and O vacancies, as well as the locally polarized electric field (PEF). The PEF and the built-in electric field (IEF) could not only accelerate carriers separation and transfer, but also enhance CO 2 adsorption and activation, thus enhancing photocatalytic activity toward CO 2 reduction. The ZZ-30%-Vw,o composite exhibited the highest CO yield of 96.91 µmol/g/h, approximately 21.0 times of the ZnSe . Moreover, the ZZ-30%-Vw,o possessed favorable structure-performance stability. The COOH* was the most important intermediate during CO 2 reduction, and possible CO 2 reduction pathways and mechanism were proposed. This work paves a feasible way for improving photocatalytic activity via introducing dual surface vacancies on heterojunction photocatalysts.