Enhanced photocatalytic efficiency by direct photoexcited electron transfer from pollutants adsorbed on the surface valence band of BiOBr modified with graphitized C

Abstract

Herein, a novel BiOBr photocatalyst with partial surface modification by graphitized C (BiOBr-C_g) was synthesized through a hydrothermal method with hydrothermal carbonation carbon (HTCC) as a slow-releasing carbon source and characterized by experimental and theoretical methods. BiOBr-C_g exhibited excellent visible-light photocatalytic performance toward various refractory pollutants, such as bisphenol A, ibuprofen, ciprofloxacin, 2,4-dichlorophenoxyacetic acid, and diphenhydramine. The characterization results demonstrate that a strong molecular orbital interaction occurs between graphitized C and BiOBr, resulting in the formation of a new surface valence band on graphitized C. This not only promotes the oxidation of pollutants by surface holes but also reduces the recombination of carriers during the bulk phase transfer process, thereby increasing the number of photogenerated carriers. Intriguingly, the analytical results for degradation intermediates and other characterization techniques demonstrate that the pollutants adsorbed on the graphitized C of BiOBr-C_g can be directly excited through light irradiation and react along the organic radical degradation pathway in addition to pollutant degradation by holes and HO₂^•/O₂^•-.

Keywords: BiOBr; Graphitized C; Pollutant adsorption; Surface valence band.