Electroreduction of Carbon Dioxide Driven by the Intrinsic Defects in the Carbon Plane of a Single Fe–N₄ Site

Abstract

Manipulating the in-plane defects of metal-nitrogen-carbon catalysts to regulate the electroreduction reaction of CO₂ (CO₂ RR) remains a challenging task. Here, it is demonstrated that the activity of the intrinsic carbon defects can be dramatically improved through coupling with single-atom Fe-N₄ sites. The resulting catalyst delivers a maximum CO Faradaic efficiency of 90% and a CO partial current density of 33 mA cm^-2 in 0.1 m KHCO_3. The remarkable enhancements are maintained in concentrated electrolyte, endowing a rechargeable Zn-CO₂ battery with a high CO selectivity of 86.5% at 5 mA cm^-2 . Further analysis suggests that the intrinsic defect is the active sites for CO₂ RR, instead of the Fe-N₄ center. Density functional theory calculations reveal that the Fe-N₄ coupled intrinsic defect exhibits a reduced energy barrier for CO₂ RR and suppresses the hydrogen evolution activity. The high intrinsic activity, coupled with fast electron-transfer capability and abundant exposed active sites, induces excellent electrocatalytic performance.