Atmosphere Induces Tunable Oxygen Vacancies to Stabilize Single-Atom Copper in Ceria for Robust Electrocatalytic CO Reduction to CH.

Electrochemical carbon dioxide reduction (ECORR) shows great potential to create high-value carbon-based chemicals, while designing advanced catalysts at the atomic level remains challenging. The ECORR 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 to methane. The obtained Cu/ceria catalyst under H environment (Cu/ceria-H) exhibits a methane Faraday efficiency (FE) of 70.03 % with a turnover frequency (TOF) of 9946.7 h at an industrial-scale current density of 150 mA cm in a flow cell. Detailed studies indicate the copious oxygen vacancies in the Cu/ceria-H 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 can markedly enhance the activation of CO, facilitate the adsorption of pivotal intermediates *COOH and *CO, thus ultimately enabling the high selectivity for CH production. This study presents deep insights into designing effective electrocatalysts for CO to CH conversion by controlling the surface microstructure via the reaction atmosphere.