Highly Efficient Electrochemical CO2 Reduction on a Precise Homonuclear Diatomic Fe-Fe Catalyst

Electrochemical CO2 reduction (ECR) to value-added chemicals offers a promising approach to mitigate net carbon emission but presents challenges for chemistry because of the high energy barrier originating from CO2 activation or product desorption, as well as the limited fundamental understanding of the reaction mechanism. Herein, a diatomic electrocatalyst with nitrogen-doped porous carbonanchored homonuclear Fe2N6 sites was precisely prepared for efficiently reducing CO2 to CO. The catalyst achieves CO Faradic efficiency up to 96.0% at -0.6 V (RHE) and a Tafel slope of only 60 mV dec-1, much superior to the single-atom Fe catalyst. Density functional theory calculations reveal that neighboring Fe-Fe centers in the Fe2N6 site facilitate the CO2 activation process via concurrently bonding the C and O atoms of the CO2 molecule. Meanwhile, the reaction barrier of CO desorption on the Fe2N6 site is decreased by the synergy of the dual Fe center, as the distinct COadsorbed configuration of the Fe2N6 site is inclined to uptake a second CO2 molecule. This work contributes fundamental understanding of ECR mechanisms and provides deep insights into the rational design of efficient ECR catalysts.