Grey Fe-CeO2-σ for boosting photocatalytic ozonation of refractory pollutants: Roles of surface and bulk oxygen vacancies

Grey Fe doped CeO2-sigma with tunable surface and bulk oxygen vacancies (OVs) were facilely prepared by a hydrothermal method. The light absorption, charge transfer efficiency, and catalytic activity and mechanism closely depended on the OVs. By tailoring the surface and bulk OVs, the catalytic activity of grey ceria was boosted due to the enhanced production of reactive oxygen species (i.e. (OH)-O-center dot, surface O). Density functional theory calculations show that the OVs, especially the bulk OVs, modulate the electronic structure for narrowing the bandgap and accelerating the charge transfer. Meanwhile, the surface OVs more promote the adsorption of ozone and the bulk OVs more induces the dissociation of ozone into reactive surface O. The calculation results agree well with the experimental observations. This study provides a simple method for engineering the surface and bulk OVs of ceria and gains insight into their roles in photocatalytic ozonation.