Shallow Trap State-Induced Efficient Electron Transfer at the Interface of Heterojunction Photocatalysts: The Crucial Role of Vacancy Defects

Constructing vacancies has been demonstrated to be an effective way to modulate charge flow in semiconductor photocatalysts. However, the role of vacancies in the interfacial electron transfer (IET) of heterojunction photocatalysts remains poorly understood, which hinders the general design of heterojunction photocatalysts. Herein, by taking g-C3N4/MoS2 as a heterojunction photocatalyst prototype, we unravel that vacancies play a critical role in the IET of heterojunction photocatalysts. Theoretical simulations, combined with femtosecond time-resolved diffuse reflectance spectroscopy, give a clear physical picture that N vacancy states act as shallow trap states (STSs) for photogenerated electrons and thereby facilitate the IET process due to a large energy difference between STSs and charge separation states. Moreover, the excess electrons left by the loss of N atoms (producing N vacancies) could partially transfer to MoS2 to generate STSs in the forbidden band of MoS2, where the transferred photogenerated electrons could be further trapped to efficiently drive H2 evolution. This work suggests a promising strategy to tune IET of heterojunction photocatalysts for achieving highly efficient photocatalytic reactions.