Photocatalytic degradation of PFOA by hydrangea-like BiOCl with high oxygen vacancies co-mediated under superoxide radicals and holes

In this study, BiOCl with a unique morphology was prepared by controlling the amount of methanol used as a solvent. The light utilization rate was improved by increasing the oxygen vacancies on the catalyst surface and changing its morphology. Oxygen vacancies and free radicals of photocatalysis were tested by ESR. The degradation mechanism of PFOA was studied by FT-IR, LC-MS, and TOC analysis of photocatalysts. The results showed that BiOCl was transformed from traditional flakes to spherical hydrangea, and the defluorination efficiency was significantly improved after adding methanol in the preparation process. Under simulated sunlight irradiation, the defluorination rate of PFOA reached 63.1 % within 30 min, which is 3.50 times higher than that of BiOCl (18.0 %) prepared without adding methanol. Mechanism studies have shown that PFOA coordinates with the catalyst surface through a single-dentate bridge, using the terminal carboxyl group. The defluorination is completed under the combined action of h+ and superoxide radical (·O2−). The oxygen vacancies on the catalyst surface promote the charge separation and the contact of PFOA, two kinds of degradation pathways also were proposed. This study introduces additional oxygen vacancies to solar-driven photocatalysts to degrade PFOA, providing a novel approach to enhance the photocatalytic defluorination of PFOA.