Interfacial Oxygen Vacancy-Copper Pair Sites on Inverse CeO2/Cu Catalyst Enable Efficient CO2 Electroreduction to Ethanol in Acid

Abstract

Renewable electricity-driven electrochemical reduction of CO₂ 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_v-Cu) pair sites are the active sites for CO₂ electroreduction to ethanol. A linear correlation between the density of O_v-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^-2 for ethanol production are achieved over the inverse CeO₂/Cu catalyst with a high density of O_v-Cu pair sites in acid. Mechanistic studies that combine density functional theory calculations and spectroscopic techniques propose an O_v-involved mechanism where interfacial O_v sites directly activate and dissociate CO₂ into *CO in a thermodynamically spontaneous manner, thus favoring the subsequent *CHO formation and asymmetric CHO-CO coupling. Besides, the asymmetric O_v-Cu pair sites could preferentially stabilize the *CH₂CHOH intermediate, resulting in the favorable formation of ethanol over ethylene. Our findings provide new atomic-level insights into CO₂ electroreduction to ethanol, paving the way for the rational design of future catalysts.

Keywords: Acidic CO2 electroreduction; catalytic mechanism; ethanol; oxygen vacancy; pair sites.