Intermediate Adsorption States Switch to Selectively Catalyze Electrochemical CO2 Reduction

Electrochemical CO2 reduction (CO2R) powered by renewable energy to convert CO2 molecules into formate is of great interest. It is still challenging to develop an efficient CO2R catalyst with high selectivity. Herein, we adjust the adsorption states of CO2– intermediates to improve the selectivity of CO2 toward formate by doping S to Cu-based electrocatalysts. It can be found that S doping could stabilize the reductive-state Cu as the active site for CO2R. The vibration models of CO2– intermediates within in situ Raman spectroscopy reveal that the selectivity improvement is ascribed to the change of the adsorption state from coexisting O*CO– and OC*O*– to the dominating OC*O*–. The electrocatalyst manifests high selectivity and activity toward formate (maximum Faradaic efficiency as high as 76.5% and maximum partial current density 21.06 mA cm–2).