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 KHCO3. 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.
Keywords: carbon dioxide reduction; carbon materials; electrocatalysis; intrinsic defects; single Fe-N 4 sites.
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