Fabrication of Cu–CeO2 Catalyst with Abundant Interfacial Cu+–O–Ce3+–OV (Oxygen Vacancy) Sites for Boosting CO2 Electroreduction to Methane

Accelerating the conversion of *CO to *CHO and promoting the adsorption and hydrogenation of *CHO are the keys to achieving a highly selective electrocatalytic CO₂ reduction reaction (CO₂RR) to CH₄ over Cu-based catalysts. Herein, a novel electrocatalyst comprising highly dispersed Cu nanoclusters (Cu_NCs) supported on oxygen vacancy (O_V)-rich CeO₂ on carbon paper (Cu_NCs–CeO₂/CP) with plentiful interfacial Cu⁺–O–Ce³⁺–O_V sites is constructed via a facile electrodeposition method. Various in situ/ex situ characterizations and theoretical calculations unveil that the Cu⁺–O–Ce³⁺–O_V sites can effectively regulate the pathway of the CO₂RR, accelerate the *CO → *CHO process, stabilize the *CHO and *OCH₃ intermediates, and promote their hydrogenation to produce CH₄. Furthermore, the critical role of Ce³⁺ and the O_V species in forming Cu⁺–O–Ce³⁺–O_V to maintain the electrocatalytic CO₂RR activity is revealed. The optimized Cu_NCs–CeO₂/CP electrocatalyst exhibits a CH₄ Faradaic efficiency of 68.3% at 500 mA cm^–2, with a high partial current density of 340 mA cm^–2.