Oxygen vacancies mediated flower-like BiOX microspheres for photocatalytic purification of methyl mercaptan odor: Significant distinction induced by halogen elements

Odor pollution, represented by low-concentration volatile organic sulfur compounds (VOSCs), has become a difficult issue in the field of air pollution control. Photocatalytic oxidation technology is applicable for the treatment of low-concentration VOSCs. However, currently available photocatalysts often suffer from limited efficiency and severe deactivation. Herein, flower-like BiOX (X = Cl, Br, I) microspheres abundant with oxygen vacancies (OVs) were developed for the removal of the model pollutant CH 3 SH. BiOI exhibited the optimal CH 3 SH oxidation performance, with the removal efficiency stabilizing at 75% within 180-min simulated solar-light irradiation, while BiOCl and BiOBr deactivated from 38% and 55% to 20% and 22%, respectively. Mechanism analysis found, OVs and I - synergistically endowed BiOI with better CH 3 SH adsorption and activation, enhanced light harvesting, quicker charge transfer, and more affluent •OH and •O 2 - productions. Photogenerated e - and •OH took a predominantly irreplaceable part in CH 3 SH oxidation, followed by •O 2 - and h + . New pathways of CH 3 SH photocatalytic oxidation was proposed, and dimethyl trisulfide was firstly found as its oxidation product. Besides, the oxidation products SO 4 2- was proved to be converted to •SO 4 - radicals to further promote CH 3 SH oxidation, and the largest production of •SO 4 - over BiOI might be responsible for its excellent performance. Furthermore, the strong adsorption and substantial accumulation of CH 3 SO 3 H on BiOCl and BiOBr might be the key cause of their rapid deactivation. This work would inspire the construction of more effective photocatalysts for the purification of VOSCs odor.