Indium Metal Oxide Tandem Ag Catalyst toward Highly Selective CO2 Electroreduction to CO over a Wide Potential Window

We report In2O3 tandem Ag-based catalysts for an electrochemical CO2 reduction reaction (eCO(2)RR), which achieve remarkable selectivity toward CO and desirable Faradaic efficiencies (FEs) exceeding 90%, with a maximum value of 97.8%, achieved over 12.25%In2O3-Ag using the H-type cell within a wide potential window ranging from -0.48 to -0.88 V vs RHE. Moreover, a high current density of -102.6 mA cm(-2) can be attained in the flow cell while maintaining an FE of CO above 90%. The theoretical calculations show a more negative Gibbs free energy for the formation of the key intermediate *CO2- on the In site, which demonstrates that In2O3 of the tandem catalyst exhibits a stronger adsorption and activation capacity for CO2. Additionally, DFT simulation reveals the thermodynamic feasibility of the surface transport of *CO2-, wherein the *CO2- intermediate migrates from the In site to the Ag site. The rapid electron transfer at the In2O3-Ag heterointerface influences the electronic environment of the Ag site, accelerating migration and reducing the energy barrier for *CO2- conversion to *COOH, ultimately facilitating the generation of CO.