Atmosphere Induces Tunable Oxygen Vacancies to Stabilize Single‐Atom Copper in Ceria for Robust Electrocatalytic CO 2 Reduction to CH 4

Abstract Electrochemical carbon dioxide reduction (ECO 2 RR) shows great potential to create high‐value carbon‐based chemicals, while designing advanced catalysts at the atomic level remains challenging. The ECO 2 RR performance is largely dependent on the catalyst microelectronic structure that can be effectively modulated through surface defect engineering. Here, we provide an atmosphere‐assisted low‐temperature calcination strategy to prepare a series of single‐atomic Cu/ceria catalysts with varied oxygen vacancy concentrations for robust electrolytic reduction of CO 2 to methane. The obtained Cu/ceria catalyst under H 2 environment (Cu/ceria‐H 2 ) exhibits a methane Faraday efficiency (FE CH4 ) of 70.03 % with a turnover frequency (TOF CH4 ) of 9946.7 h −1 at an industrial‐scale current density of 150 mA cm −2 in a flow cell. Detailed studies indicate the copious oxygen vacancies in the Cu/ceria‐H 2 are conducive to regulating the surface microelectronic structure with stabilized Cu + active center. Furthermore, density functional theory calculations and operando ATR‐SEIRAS demonstrate that the Cu/ceria‐H 2 can markedly enhance the activation of CO 2 , facilitate the adsorption of pivotal intermediates *COOH and *CO, thus ultimately enabling the high selectivity for CH 4 production. This study presents deep insights into designing effective electrocatalysts for CO 2 to CH 4 conversion by controlling the surface microstructure via the reaction atmosphere.