Crystal-Plane Effects of CeO2{110} and CeO2{100} on Photocatalytic CO2 Reduction: Synergistic Interactions of Oxygen Defects and Hydroxyl Groups

For photocatalytic CO2 reduction, the synergistic effect of Lewis acidity and basicity on CO2 activation is worthy of study. On the basis of a large number of oxygen defects (Lewis acidity) and hydroxyl groups (Lewis basicity) on the CeO2 surface, CeO2{110} and CeO2{100} crystal planes were developed to investigate the synergistic effect on photocatalytic CO2 reduction. Compared with CeO2{100}, the surface oxygen defects were prone to generate on CeO2{110}, leading to available visible light absorption and faster photogenerated charge transfer. The experimental results and DFT calculations showed that the OH species on the CeO2{110} surface were richer and provided more electron density, i.e., Lewis basicity. Furthermore, the possible adsorption intermediate was investigated and suggested that CeO2{110} was more beneficial for the adsorption and activation of CO2 reactant than CeO2{100}, resulting in generation of carboxylate species and •CO2– radicals, instead of carbonate. Under the control of surface Lewis acidity and basicity, CeO2{110} had superior photocatalytic performance of CO2 reduction than the {100} plane.