Regulating the delocalization of Bi 6p orbital by halide doping in BiOCl for excellent photocatalytic performance

Activation of inert molecules and stabilization of intermediates during photocatalytic reactions in Bi-based photocatalysts can be achieved by shifting the band center of Bi 6p orbital but the underlying mechanism requires further investigation. Herein, halogen-doping BiOCl photocatalysts were synthesized using a simple solvothermal method and experimental results showed that BiOCl_0.4Br_0.6 and BiOCl_0.8I_0.2 photocatalysts not only achieved a maximum CO evolution rate of 270 and 227 µL·g^-1·h^-1 with a high selectivity of 97 %, but also effectively removed environmental pollutants. Density functional theory calculations demonstrate that halogen-doping shifted the band center of the Bi 6p orbital in BiOCl towards the Fermi level, leading to the delocalization of the Bi 6p orbital. This is of great importance to activate O₂, CO₂, and Cr₂O₇^2- adsorbed on the catalyst surface, as well as stabilize the *COOH intermediate and lower the energy barrier of key steps in highly selective photoreduction of CO₂ to CO.