Creating abundant oxygen vacancies in CeO2 by plasma-etching to enhance catalytic ozonation: An efficient degradation relying on surface oxidation pathway

Herein, plasma etching was applied to prepare the CeO2 of abundant oxygen vacancies (OVs) for excellent catalytic ozonation of oxalic acid (OA). After plasma etching with atmosphere of O2 for 15 min, the modified CeO2 (O-CeO2-15) significantly enhanced the elimination of OA to 47.15 % within 60 min at the pH of 7.15. The COD was reduced by 20 mg/L, 1.7 times that of pristine CeO2 catalytic ozonation. The adsorption of O3 by OCeO2-15 was twice that of the pristine CeO2. Raman, XPS, H2-TPR and CV characterization results magnified that O-CeO2-15 had abundant oxygen vacancies (OVs) and great reducibility. The theoretical calculation results demonstrated that the O3 adsorbed on the OVs was converted to center dot O3 by electron transfer, which leaded to chain reaction to generate Reactive oxygen species (ROS), and part of O3 was decomposed into *O as the main ROS to degrade OA. This study provided a convenient and eco-friendly enhanced OVs method and gained a different insight into the mechanism of CeO2 degradation of pollutants.