Highly Active Oxygen Coordinated Configuration of Fe Single-Atom Catalyst toward Electrochemical Reduction of CO₂ into Multi-Carbon Products

Electrochemical reduction of carbon dioxide (CO2RR) into value-added chemicals is a promising tactic to mitigate global warming. However, this process resists catalyst preparation, low faradaic efficiency (FE%) towards multi-carbon products, and insights into mechanistic understanding. Indeed, it is demonstrated that this Fe single-atom catalyst (Fe SAC) exists in three oxygen coordination of Fe-(O)(3) configuration in Nafion coated functionalized multi-wall carbon nanotubes (Fe-n-f-CNTs), which is obtained via a simple ionic exchange method under ambient conditions. The electrochemical performance reveals that Fe SACs achieve an FE of 45% and a yield rate of 56.42 mu mol cm(-2) h(-1) at -0.8 V-RHE for ethanol. In situ X-ray analysis reveals that the Fe SACs have variable electronic states and keeps close +3 of the oxidation state at the potential range of CO2RR. The catalytic feature reduces the reaction energy and induces the electrons transferred to the adsorbed products intermediates of *COOH and *OCHO, thus promoting CO. The carboxylic functional group on the CNTs stabilizes the Fe active sites via electrostatic interaction, verified by density functional theory calculations. The yield rate of Fe SACs indicates that the Fe single-atom site can instantly provide a large CO to help conversion of CO2-to-C-2 product on the CNTs.