New insights into the role of sulfite in BiOX photocatalytic pollutants elimination: In-operando generation of plasmonic Bi metal and oxygen vacancies.

Photocatalysis has been regarded as a sustainable strategy for wastewaters remediation, and sulfite addition could significantly accelerate the photocatalytic performances. However, the related mechanisms are still not well understood. Here, we for the first time found that plasmonic Bi and oxygen vacancies were in-operando generated on BiOX (X = Cl, Br, I) in the presence of sulfite under light irradiation. The oxidative degradation rate constants of 4-nitrophenol, bisphenol A, and phenol were improved by about 11.5, 4.7, and 12.2 times on BiOBr and 9.1, 1.6, and 3.1 times on BiOCl with addition of 5 mM sulfite, while the photocatalytic reduction rate of 4-nitrophenol to 4-aminophenol was promoted by approximate 31.7 times on BiOI. The results indicated that sulfite could improve the photooxidation ability of BiOBr and BiOCl and the photoreduction performance of BiOI, resulted from the improved light absorption and separation of photogenerated charge carriers. This work can provide exploratory platforms for understanding and maximizing the sulfite-assisted BiOX photocatalysis.