Low overpotential electrochemical CO2 reduction to formate on Co3O4-CeO2/low graphitic carbon catalyst with oxygen vacancies

We report a strategy to reduce the overpotential of CO2 electrocatalytic reduction (CO2ER) into formate by fabrication of on Co3O4-CeO2/low graphitic carbon (LGC) with oxygen vacancies. Experimental results showed that the overpotential of CO2ER into formate on Co3O4-CeO2/LGC electrode was only -0.31 V vs. RHE, and the maximum FEformate was 76.4% at -0.75 V vs RHE (-6.1 mA square cm(-2)) with desirable stability of 45 h, displaying the maximum formate rate of 1.6 mmol square m(-2) square s(-1)square C-1 square mg(-1). X-ray photoelectron spectroscopy (XPS) combined with energy-dispersive X-ray spectroscopy (EDS) measurements showed that the addition of Co3O4 into CeO2/LGC led to highly concentrated oxygen vacancies that were found to be key in the enhanced activity and stable formate selectivity and the inhibited hydrogen evolution reaction (HER). Furthermore, DFT calculation demonstrated that the oxygen vacancies can effectively enhance the activation of CO2 and promote the electrochemical CO2 reduction along CO2 -> CO2* -> COOH* -> HCOOH path.