Vacancy Defects Engineering in Yolk-shelled Co-CeO2 for Efficient Visible Light-Driven CO2 Reduction

Solar-driven photocatalytic CO2 conversion is considered as the most promising approach to eliminating atmospheric CO2 emissions. However, great challenges lie in the utilization of visible-infrared light and the activation of the inert CO2 molecule. Herein, we report the preparation of a yolk-shell Co-CeO2 octahedron and the strategy for surface defect engineering to optimize the photocatalyst by two-step calcination of a Ce-based metal-organic framework (Ce-UiO-66). As a result of the synergistic effect of incorporating the Co atom and rich oxygen vacancies, the energy barrier of activating and transforming the adsorbed CO2 to *COOlH is significantly reduced. Benefiting from the structure with high surface area, cavity, and abundant defects, the optimized Co-CeO2 photocatalyst not only provides more exposed active sites and enhanced photoabsorption but also improves charge separation and transfer. Accordingly, 1%-Co-CeO2-H-2 exhibits much higher photocatalytic activity in CO2 reduction under visible light irradiation with a CO generation rate of 46.9 mu mol/h, which is 4.6 times than that of less defective 1%-Co-CeO2, and far more than that of pure CeO2.