Operando evidence of Cu+ stabilization via a single-atom modifier for CO2 electroreduction†
Oxide-derived Cu materials are most commonly used as electrocatalysts for the carbon dioxide reduction reaction (CO2RR). Previous studies have proved that Cu+ and residual subsurface oxygen species can enhance the CO2RR activity; however the stable presence of Cu+ remains a subject of debate. Here, we design a strategy of single-atom Sn anchored on Cu2O nanosheets to stabilize the key Cu+ species for electroreduction of CO2. Operando synchrotron X-ray absorption spectroscopy and statistics analysis distinguish the active Cu+ and reduced Cu+ species, and reveal that the constructed Sn–O–Cu sites with charge transfer can significantly enhance the resistance of copper oxides to reduction. Operando infrared spectroscopy suggests that the survival of Cu+ species on the catalyst surface promotes the adsorption of *CO during the CO2RR, leading to the obvious improvement of CO2-to-CO conversion. Our results demonstrate the role of a single-atom-modifier in both stabilizing Cu+ species and enhancing the CO2RR selectivity of oxide-derived Cu catalysts.