Unraveling the Mechanism of Cu/CeO2 Interface Modulation for CO2 Electroreduction Into C2+/CH4

Cu shows unique characteristics for electrochemical CO 2 reduction reaction (CO 2 RR) to hydrocarbons and oxygenates due to the moderate adsorption energy of the key intermediate *CO. However, it remains a challenge to selectively control CO 2 RR towards C 1 (e.g., CH 4 ) or C 2+ (e.g., C 2 H 4 and C 2 H 5 OH) through simple interface engineering. Herein, a series of inverse catalysts, composed of CeO 2 nanoparticles over Cu substrate (Cu-CeO 2 -x), are subtly designed to tackle the issues. It is verified CeO 2 decoration induces highly active Cu/CeO 2 interfacial sites that enhance the adsorption and conversion of CO 2 and *CO intermediates into C 2+ or CH 4 , while the Cu sites are conducive to *CO generation. With the increase of CeO 2 deposition, the C 2+ and CH 4 selectivity present a volcano-type and increasing tendency with maximum faradic efficiency of 62.6% and 51.3%, respectively. In-situ infrared spectroscopy and theoretical calculations reveal that moderate CeO 2 loading allows the Cu/CeO 2 interfacial sites to cooperate efficiently with the Cu sites to promote the coupling of *CO/*CHO intermediates, thus enhancing the C 2+ selectivity. In contrast, excessive CeO 2 loading suppresses the C─C coupling but boosts unilaterally the hydrogenation, thus promoting the CH 4 production. This work provides effective strategies to regulate the CO 2 RR selectivity by modulating metal/oxide interfaces.