Time-controlled oxygen vacancy engineering in CeO2 for efficient photocatalytic CO2 reduction

Here, we report a one-pot ethylene glycol solvothermal approach to tune Oxygen vacancies (OVs) concentration in CeO 2 nanocrystals simply by adjusting the reaction time from 6 to 24 h. The OV density follows a volcano-shaped evolution, peaking at 12 h, accompanied by a morphology transition from nanospheres to nanorods. The optimized CeO 2 –12 h sample exhibits significantly enhanced CO evolution (29 μmol g −1 h −1 ) and selective CO 2 -to-fuel conversion, outperforming the 6 h and 24 h counterparts. Comprehensive characterization reveals that the superior activity originates from the synergistic effects of maximized OVs, favorable nanorod morphology, and improved charge separation. In-situ DRIFTS identifies carbonate and formate as key intermediates, elucidating the vacancy-mediated reaction pathway. This work establishes a direct time–defect–activity relationship and demonstrates that moderate defect engineering is the key to unlocking high-performance CO 2 photoreduction.