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

Electron transfer to CO2 is commonly regarded as a critical step for activating CO2. Herein, we describe the development of a simple and effective strategy to facilitate electron transfer to CO2 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 CO2 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 (Bu4NCl/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 CO2. 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 CO2 molecules, resulting in activating CO2 and forming the key CO2 center dot- radical.