Oxygen vacancies in oxide-derived EGaIn enhance CO2 electrochemical reduction to CO in organic electrolyte

Electron transfer to CO 2 is commonly regarded as a critical step for activating CO 2 . Herein, we describe the development of a simple and effective strategy to facilitate electron transfer to CO 2 by introducing oxygen vacancies (O V ) in electrocatalysts. We discovered that stirring oxidized eutectic gallium indium is an important pretreatment step for introducing O V . In the subsequent CO 2 reduction process, the oxidized eutectic gallium indium (O-EGaIn) was reduced to the oxide-derived EGaIn (OD-EGaIn), which achieved 4 times higher Faradic efficiency for CO production than the eutectic gallium indium (EGaIn) in a tetrabutylammonium chloride/acetonitrile (Bu 4 NCl/AN) electrolytes. The XPS results showed that the O V concentration in the OD-EGaIn is much larger than that in the O-EGaIn and EGaIn samples. Electrokinetic studies indicated that the introduction of O V facilitates electron transfer to CO 2 . Density functional theory (DFT) calculations further revealed that the electrons tend to accumulate around the O V . These localized electrons then flow to the antibonding orbitals of CO 2 molecules, resulting in activating CO 2 and forming the key CO 2 •− radical.