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

Abstract

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 (OV) in electrocatalysts. We discovered that stirring oxidized eutectic gallium indium is an important pretreatment step for introducing OV. 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 OV concentration in the OD-EGaIn is much larger than that in the O-EGaIn and EGaIn samples. Electrokinetic studies indicated that the introduction of OV facilitates electron transfer to CO2. Density functional theory (DFT) calculations further revealed that the electrons tend to accumulate around the OV. These localized electrons then flow to the antibonding orbitals of CO2 molecules, resulting in activating CO2 and forming the key CO2•− radical.