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

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 (OV) 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 OV 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.