Overall Regulation of Exciton Dynamics by Defect Engineering in Polymeric Photocatalysts for Hydrogen Evolution

For photocatalysts with a strong exciton effect, overall understanding and regulating exciton dynamics, which is central to optimizing performance, have been ignored. Herein, taking a carbon nitride derivative as the model system, we demonstrate the alteration of multiple band structures for regulating the overall exciton dynamics and accordingly the photocatalytic hydrogen evolution performance by introducing cyano defects. Both experimental and theoretical data show that with increasing defect concentration, the defect-mediated trap state (TS) increases the singlet exciton generation, facilitates the exciton transfer from the first singlet excited state to TS rather than to the triplet excited state, promotes exciton dissociation, and suppresses the singlet exciton recombination until reaching to the highest activity. However, excess defects will act as recombination centers, leading to severe exciton recombination and decreased activity. This work provides a new insight into an in-depth understanding of comprehensive regulation of exciton dynamics for high-efficiency solar energy conversion.