Fabrication\nof Cu–CeO<sub>2</sub> Catalyst\nwith Abundant Interfacial Cu<sup>+</sup>–O–Ce<sup>3+</sup>–O<sub>V</sub> (Oxygen Vacancy) Sites for Boosting CO<sub>2</sub> Electroreduction to M

Accelerating the conversion of *CO to *CHO and promoting\nthe adsorption\nand hydrogenation of *CHO are the keys to achieving a highly selective\nelectrocatalytic CO<sub>2</sub> reduction reaction (CO<sub>2</sub>RR) to CH<sub>4</sub> over Cu-based catalysts. Herein, a novel electrocatalyst\ncomprising highly dispersed Cu nanoclusters (Cu<sub>NCs</sub>) supported\non oxygen vacancy (O<sub>V</sub>)-rich CeO<sub>2</sub> on carbon paper\n(Cu<sub>NCs</sub>–CeO<sub>2</sub>/CP) with plentiful interfacial\nCu<sup>+</sup>–O–Ce<sup>3+</sup>–O<sub>V</sub> sites is constructed via a facile electrodeposition method. Various <i>in situ</i>/<i>ex situ</i> characterizations and theoretical\ncalculations unveil that the Cu<sup>+</sup>–O–Ce<sup>3+</sup>–O<sub>V</sub> sites can effectively regulate the\npathway of the CO<sub>2</sub>RR, accelerate the *CO → *CHO\nprocess, stabilize the *CHO and *OCH<sub>3</sub> intermediates, and\npromote their hydrogenation to produce CH<sub>4</sub>. Furthermore,\nthe critical role of Ce<sup>3+</sup> and the O<sub>V</sub> species\nin forming Cu<sup>+</sup>–O–Ce<sup>3+</sup>–O<sub>V</sub> to maintain the electrocatalytic CO<sub>2</sub>RR activity\nis revealed. The optimized Cu<sub>NCs</sub>–CeO<sub>2</sub>/CP electrocatalyst exhibits a CH<sub>4</sub> Faradaic efficiency\nof 68.3% at 500 mA cm<sup>–2</sup>, with a high partial current\ndensity of 340 mA cm<sup>–2</sup>.