Single-Atom Iron-Nitrogen Catalytic Site with Graphitic Nitrogen for Efficient Electroreduction of CO₂

Electrochemical reduction of CO₂ to carbon monoxide (CO) and other useful fuels/chemicals offers a green and promising technical solution for alleviating greenhouse effect and creating economic benefits. Herein, we developed a single-atom Fe dispersed on N-doped carbons nanosheet (Fe−SA/NCS−X) for CO₂ electroreduction by direct pyrolysis of hemin-doped polyaniline fabricated by in-situ chemical polymerization. The Fe-SA/NCS-700 achieved a Faraday efficiency of CO up to 87 % at −0.45 V vs. RHE, a low onset overpotential of 105 mV and remarkable durability with the current density being maintained for 10 h constant electrocatalysis, which were comparable to the latest reported single-atom catalysts. The Tafel slope of Fe-SA/NCS-700 was measured to be about 67 mV/dec, close to theoretical value of 59 mV/dec, which indicated a rapid pre-equilibrating one-electron transfer followed by a rate-determining reaction step. DFT calculations revealed that the graphitic N species can synergistically improve the catalytic activities of Fe-N₄ sites of Fe-SA/NCS−X by significantly lowering the free energy barriers of *COOH intermediate formation, thus promoting CO₂ electroreduction to CO.