Tuning oxygen vacancy for efficient CO2 electroreduction over CeO2 supported SnO2

CO2 electroreduction is favorable in neutral or alkaline aqueous solutions, where H2O serves as the proton source, suffering from sluggish dynamics. Herein, we synthesize a series of SnO2-CeO2 with different oxygen vacancy (Ov) concentration, regulating the H2O dissociation, to synchronize with the CO2 reduction. The optimal SnO2-CeO2 catalyst, with a moderate Ov concentration, exhibits a formate Faradic efficiency of nearly 93% and maintains for more than 46 h at a current density of 100 mA/cm2. The catalyst with lower Ov concentration results in weak H2O dissociation, thus enhancing the energy barrier of *OCHO generation, while higher Ov concentration leads to excessive proton, exacerbating the hydrogen evolution reaction (HER), as supported by DFT calculation and in situ attenuated total reflection-Fourier transform infrared spectra (ATR-FTIR). This study underscores the significance of Ov concentration in determining the ability of water dissociation over supported electrocatalysts, providing valuable insights for the development of more efficient electrocatalyst.