Vacancy-induced Fermi level shifts for heterojunction reconstruction boosting photocatalytic hydrogen evolution

Although conventional Type-I heterojunctions can spatially confine photogenerated charge carriers, the low charge separation efficiency often compromises the redox capability of the carriers, thereby limiting their applications in high-efficiency reduction reactions such as photocatalytic hydrogen evolution. In this study, we propose a novel strategy involving vacancy engineering to modulate the Fermi level of ZnS, thereby enabling the reconstruction of heterojunction types between ZnS and CdS from the original Type-I into a staggered Z-scheme configuration. Under simulated sunlight irradiation, the vacancy-tailored Z-scheme V-ZnS/CdS heterojunction achieved a hydrogen evolution rate 3.2 times higher than that of the Type-I heterojunction, along with excellent cycling stability. This study not only provides a paradigm for modulating heterojunction types through defect engineering, but also opens a new avenue for designing artificial photosynthetic systems that combine high charge separation efficiency with strong redox capability.