Local structure tuning in Fe-N-C catalysts through support effect for boosting CO2 electroreduction

Abstract

Metal-N-C materials have attracted considerable attention for electrocatalytic CO2 reduction. Local electronic and geometric structure of active sites in the metal-N-C catalysts significantly determine catalytic reactivity. In this work, atomically dispersed Fe species with different coordination environment are anchored into carbon supports through introducing aminated carbon nanotubes, as effectively revealed by the Cs-corrected transmission electron microscope and X-ray absorption near edge structure spectra. Electrochemical tests show that the catalyst with the aminated carbon nanotubes has a low overpotential (0.39 V) and high selectivity of CO up to 95.47 % at -0.6 V vs. RHE. The density functional theory calculation results indicate that the additional axial Fe-N coordination compared with the planar Fe-N coordination can reduce the free energy required for the desorption of CO from the adsorption site and inhibit the occurrence of hydrogen evolution reaction, thus leading to improve the selectivity of CO.