A Graphene-Supported Single-Atom FeN5 Catalytic Site for Efficient Electrochemical CO2 Reduction.

Abstract

Electrochemical conversion of CO2 into valued products is one of the most important issues but remains a great challenge in chemistry. Herein, we report a novel synthetic approach involving prolonged thermal pyrolysis of hemin and melamine molecules on graphene for the fabrication of a robust and efficient single-iron-atom electrocatalyst for electrochemical CO2 reduction. The single-atom catalyst exhibits high Faradaic efficiency (ca. 97.0 %) for CO production at a low overpotential of 0.35 V, outperforming all Fe-N-C-based catalysts. The remarkable performance for CO2 -to-CO conversion can be attributed to the presence of highly efficient singly dispersed FeN5 active sites supported on N-doped graphene with an additional axial ligand coordinated to FeN4 . DFT calculations revealed that the axial pyrrolic nitrogen ligand of the FeN5 site further depletes the electron density of Fe 3d orbitals and thus reduces the Fe-CO π back-donation, thus enabling the rapid desorption of CO and high selectivity for CO production.