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

Abstract

We report In 2 O 3 tandem Ag-based catalysts for an electrochemical CO 2 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%In 2 O 3 − 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 *CO 2 − on the In site, which demonstrates that In 2 O 3 of the tandem catalyst exhibits a stronger adsorption and activation capacity for CO 2 . Additionally, DFT simulation reveals the thermodynamic feasibility of the surface transport of *CO 2 − , wherein the *CO 2 − intermediate migrates from the In site to the Ag site. The rapid electron transfer at the In 2 O 3 −Ag heterointerface influences the electronic environment of the Ag site, accelerating migration and reducing the energy barrier for *CO 2 − conversion to *COOH, ultimately facilitating the generation of CO.