Aliovalent Cl Substitution Modulates Oxygen‐Vacancy‐Related Defect States in Bi 2 O 2 S Toward Efficient Photocatalytic CO 2 ‐to‐CO Conversion

Abstract

Pristine Bi 2 O 2 S suffers from pronounced surface inertness and inefficient utilization of photogenerated charge carriers in photocatalytic CO 2 reduction. To address this limitation, an aliovalent Cl‐for‐S substitution strategy is employed. Owing to the comparable ionic sizes of Cl − and S 2− , Cl incorporation largely preserves the host crystal framework while modulating oxygen‐vacancy‐related defect states, modifying the electronic structure, and promoting photogenerated charge separation and migration. As a result, the optimized Cl‐BOS‐0.6 catalyst achieves a CO evolution rate of 59.6 μmol g −1 ·h −1 , corresponding to an approximately 18.6‐fold enhancement over pristine Bi 2 O 2 S, together with good stability and CO selectivity. In situ spectroscopic characterizations and density functional theory calculations further indicate a coupled dopant–defect effect that promotes local charge redistribution and differentiated adsorption of CO 2 and H 2 O, thereby facilitating efficient and selective photocatalytic CO 2 ‐to‐CO conversion. This work provides a viable strategy for regulating the local electronic structure and defect chemistry of Bi 2 O 2 S‐based photocatalysts and offers new insight into the rational design of efficient CO 2 photoreduction materials.