Hydroxy-Group-Enriched In2O3 Facilitates CO2 Electroreduction to Formate at Large Current Densities

The development of catalysts and electrochemical systems for CO2 electroreduction has achieved substantial progress recently, while the long-time operation of electrolyzing CO2 to formate with high activity and selectivity remains as a major challenge, due to the continuous carbonate precipitation at elevated pHs. Herein, hexagonal phase In2O3 (h-In2O3) is demonstrated with a monodispersed porous nanosphere structure that can serve as an efficient electrocatalyst for converting CO2 to formate, with a peak Faradaic efficiency of 98%, high partial current densities for producing formate, and outstanding electrochemical stability, substantially exceeding cubic phase In2O3 and most of the previously reported electrocatalysts. Both experimental and theoretical studies reveal that the excellent activity and stability are attributed to the enhanced adsorption and activation of CO2 on the h-In2O3 surface, and the rich surface hydroxyl groups further facilitate the inhibition of carbonate formation. This work suggests attractive features of the phase engineering to modulate surface hydroxyl groups for efficient and robust catalysts for CO2 electroreduction.