Engineering Oxygen Vacancy in Support to Promote Activity of In ₂ O ₃ Catalyst for CO ₂ Electroreduction to Formate

Abstract The electrocatalytic CO ₂ reduction reaction (CO ₂ RR) to formate offers an economical and effective strategy for CO ₂ conversion and storage. Indium (In) based catalysts exhibit high activity and selectivity for formate production; however, their performance still requires enhancement to meet these goals. A novel approach is proposed by depositing In ₂ O ₃ onto an oxygen vacancy (O _V )‐enriched support, ceria‐zirconia solid solutions (CZ), to activate synergistic effects. The O _V concentration in CZ support is effectively adjusted by controlling the Ce concentration. Electrochemical tests show that In ₂ O ₃ loaded on CZ with the highest O _V concentration (In ₂ O ₃ /CZ‐r), achieving an impressive current density (165 mA cm ⁻² ) and a Faradaic efficiency for formate of 95.3% at −1.27 V versus RHE. Notably, In ₂ O ₃ /CZ‐r also maintains its excellent CO ₂ RR performance under low CO ₂ concentrations and a wide pH range. Further insights into the mechanism of CO ₂ RR reveal that the O _V contributes greatly to the dissociation of H ₂ O and further promotes the hydrogenation of adsorbed CO ₂ species. Consequently, the reaction energy barrier for formate production is reduced and CO ₂ RR activity is improved significantly. This study provides significant insights into the development of efficient CO ₂ RR catalysts through strategic engineering of O _V in support materials, thereby enhancing catalytic performance through synergistic interactions.