Regulating charge dynamics in single-crystalline Bi₂O₂Se nanosheets via oxygen vacancy engineering for efficient...

Bi₂O₂Se is an emerging layered semiconductor with excellent charge-transport properties and environmental stability, making it a promising photocatalyst for environmental remediation. Herein, single-crystalline Bi₂O₂Se nanosheets with tunable oxygen-vacancy (O_V) concentrations were successfully synthesized via a facile hydrothermal route followed by hydrogen annealing to optimize their intrinsic photocatalytic activity. The optimized sample (Bi₂O₂Se 600) exhibited markedly enhanced photocatalytic performance, achieving degradation efficiencies of 94.90% for Congo red (CR) within 40 min and 87.03% for tetracycline (TC) within 60 min, with corresponding degradation rate constants 23.6 and 3.3 times higher than those of pristine counterpart, respectively. Spectroscopic and electrochemical analyses demonstrated that O_V engineering effectively enhanced charge-carrier dynamics by suppressing electron-hole recombination and promoting interfacial charge transfer. Radical-trapping experiments combined with electron paramagnetic resonance (EPR) measurements identified ·O₂^- as the dominant reactive species responsible for pollutant degradation. In addition, Bi₂O₂Se 600 maintained excellent photocatalytic activity across different water matrices and exhibited outstanding cycling stability. This work presents an effective strategy for combine single-crystal engineering with oxygen-vacancy regulation to optimize charge-carrier dynamics, providing new insights into the rational design of high-performance photocatalysts for environmental remediation.