Tailoring Isolated Cu-N4 and Fe-N4 Atomic Sites for Efficient Selective Electroreduction of CO2 to CO

Abstract

The electrochemical reduction of CO2 to CO represents a critical pathway for carbon-neutral energy cycles, yet designing catalysts that simultaneously achieve high activity, selectivity, and durability remains challenging. Herein, we report a Cu−Fe dual single-atom catalyst (Cu-FeSA) anchored on a ZIF-8-derived nitrogen-doped carbon matrix, in which atomically dispersed Cu−N4 and Fe−N4 sites act synergistically to enhance electrochemical CO2 reduction reaction (CO2RR) performance. The Cu-FeSA catalyst exhibits a low onset potential of −0.36 V (vs. RHE) and achieves a CO Faradaic efficiency (FECO) of 95% with a partial current density of 9.5 mA cm−2 and a CO production rate of 155.8 mmol h−1 gcat−1 in an H-cell system. In a flow cell, it maintains nearly 100% FECO over 10 h without significant degradation. Density functional theory (DFT) simulations reveal that the Fe−Cu−N4 dual-site structure lowers the energy barrier for *CO2 formation compared to Fe−N4 and Cu−N4, promoting CO2 activation. Moreover, the free energy of *CO desorption on Fe−Cu−N4 is significantly higher than on Fe−N4, facilitating CO release. These results indicate that the Cu sites optimize *COOH adsorption, while the Fe sites enhance proton-coupled electron transfer, collectively suppressing the hydrogen evolution reaction (HER). This work provides a mechanistic basis for the rational design of dual-atom catalysts for efficient CO2-to-CO conversion.