New insight into the visible-light-driven photoinduced electron transfer mechanism for ozone activation over defective sites of ceria for organic compounds destruction

Herein, we prepared CeO2 with varying concentrations of oxygen vacancies (Ov) and investigated the effects of the Ov concentration and photoinduced electron transfer (PET) on O3 activation under visible-light-driven (VLD) photocatalytic-ozonation (PO) for removal of oxalic acid (OA). Density functional theory calculations showed the formation of Ov reduced the bandgap of CeO2, leading to region around the Ce atom with a low adsorption energy barrier toward O3. Notably, no distinct linear correlation was found between the Ov concentration and VLD-PO activity. This implies that CeO2 with a lower amount of Ov (14.64%) exhibits better PET and higher photoexcited electron density than CeO2 with a relatively higher Ov (17.62%), suggesting that the PET properties of CeO2 are crucial for the Ov regeneration and O3 activation and conversion for OA removal. Electric energy per order (EEO) for VLD-PO using CeOx(7 0 0) was 6.94 kWh m−3 order−1. Additionally, bioassay experiments with Daphnia Magna showed toxicity reduction in the PO-treated effluent and continuous-flow experiments (CFEs) proved that VLD-PO could effectively remediate the toxic and refractory micropollutants containing water. The study findings can promote the application of PO systems in water treatment for treating organic pollutants.