Interfacial Oxygen Vacancy-Copper Pair Sites on Inverse CeO/Cu Catalyst Enable Efficient CO Electroreduction to Ethanol in Acid.

Renewable electricity-driven electrochemical reduction of CO offers a promising route for the production of high-value ethanol. However, the current state of this technology is hindered by low selectivity and productivity, primarily due to a limited understanding of the atomic-level active sites involved in ethanol formation. Herein, we identify that the interfacial oxygen vacancy-neighboring Cu (O-Cu) pair sites are the active sites for CO electroreduction to ethanol. A linear correlation between the density of O-Cu pair sites and ethanol productivity is experimentally evidenced. Moreover, a high Faradaic efficiency of 48.5 % and a partial current density of 344.0 mA cm for ethanol production are achieved over the inverse CeO/Cu catalyst with a high density of O-Cu pair sites in acid. Mechanistic studies that combine density functional theory calculations and spectroscopic techniques propose an O-involved mechanism where interfacial O sites directly activate and dissociate CO into *CO in a thermodynamically spontaneous manner, thus favoring the subsequent *CHO formation and asymmetric CHO-CO coupling. Besides, the asymmetric O-Cu pair sites could preferentially stabilize the *CHCHOH intermediate, resulting in the favorable formation of ethanol over ethylene. Our findings provide new atomic-level insights into CO electroreduction to ethanol, paving the way for the rational design of future catalysts.