Atomic Indium Catalysts for Switching CO$_2$ Electroreduction Products from Formate to CO

Electrochemical reduction of CO$_2$ to chemicals and fuels is an interesting and attractive way to mitigate greenhouse gas emissions and energy shortages. In this work, we report the use of atomic In catalysts for CO$_2$ electroreduction to CO. The atomic In catalysts were anchored on N-doped carbon (InA/NC) through pyrolysis of In-based metal–organic frameworks (MOFs) and dicyandiamide. It was discovered that InA/NC had outstanding performance for selective CO production in the mixed electrolyte of ionic liquid/MeCN. It is different from those common In-based materials, in which formate/formic acid is formed as the main product. The faradaic efficiency (FE) of CO and total current density were 97.2% and 39.4 mA cm$^{–2}$, respectively, with a turnover frequency (TOF) of ∼40 000 h$^{–1}$. It is one of the highest TOF for CO production to date for all of the catalysts reported. In addition, the catalyst had remarkable stability. Detailed study indicated that In$_A$/NC had higher double-layer capacitance, larger CO$_2$ adsorption capacity, and lower interfacial charge transfer resistance, leading to high activity for CO$_2$ reduction. Control experiments and theoretical calculations showed that the In–N site of In$_A$/NC is not only beneficial for dissociation of COOH* to form CO but also hinders formate formation, leading to high selectivity toward CO instead of formate