Pore-Edge Tailoring of Single-Atom Iron–Nitrogen Sites on Graphene for Enhanced CO₂ Reduction

Abstract

Hosting atomically dispersed nitrogen-coordinated iron sites (Fe-N<sub>4</sub>) on graphene offers unique opportunities for driving electrochemical CO<sub>2</sub> reduction reaction (CO<sub>2</sub>RR) to CO. However, the strong adsorption of *CO on the Fe-N<sub>4</sub> site embedded in intact graphene limits current density due to slow CO desorption process. Herein, we report how the manipulation of pore edges on graphene alters the local electronic structure of isolated Fe-N<sub>4</sub> sites and improves their intrinsic reactivity for prompting CO generation. We demonstrate that constructing holes on graphene basal plane to support Fe-N<sub>4</sub> can significantly enhance its CO<sub>2</sub>RR compared to the pore-deficient graphene-supported counterpart, exhibiting a CO Faradaic efficiency of 94% and a turnover frequency of 1630 h<sup>-1</sup> at 0.58 V vs RHE. Mechanistic studies reveal that the incorporation of pore edges results in the downshifting of the d-band center of Fe sites, which weakens the strength of the Fe-C bond when the *CO intermediate adsorbs on edge-hosted Fe-N<sub>4</sub>, thus boosting the CO desorption and evolution rates. These findings suggest that engineering local support structure renders a way to design high-performance single-atom catalysts.