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 (O_v) and investigated the effects of the O_v 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 O_v 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 O_v concentration and VLD-PO activity. This implies that CeO₂ with a lower amount of O_v (14.64%) exhibits better PET and higher photoexcited electron density than CeO₂ with a relatively higher O_v (17.62%), suggesting that the PET properties of CeO₂ are crucial for the O_v regeneration and O₃ activation and conversion for OA removal. Electric energy per order (EEO) for VLD-PO using CeO_x(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.