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).