Unraveling in-situ electrochemical reconstruction of indium oxide catalysts with oxygen vacancy for enhanced electrocatalytic CO2-to-formate conversion

• The In/In2O3-VO configuration exhibits the lowest energy barrier (0.99 eV) for CO2 reduction to formate. • An air-annealing strategy applied to In3+-adsorbed resin yields indium oxide catalysts with abundant oxygen vacancies (R-In2O3). • In-situ spectroscopy confirms electrochemical reconstruction into In/In2O3 and stabilization of the HCOO* intermediate. • R-In2O3 maintains >92% current efficiency for CO2-to-formate over 56 h at −250 mA·cm−2, demonstrating durable performance.