The built-in electric field across FeN/Fe₃N interface for efficient electrochemical reduction of CO₂ to CO

Nanostructured metal-nitrides have attracted tremendous interest as a new generation of catalysts for electroreduction of CO₂, but these structures have limited activity and stability in the reduction condition. Herein, we report a method of fabricating FeN/Fe₃N nanoparticles with FeN/Fe₃N interface exposed on the NP surface for efficient electrochemical CO₂ reduction reaction (CO₂RR). The FeN/Fe₃N interface is populated with Fe-N₄ and Fe-N₂ coordination sites respectively that show the desired catalysis synergy to enhance the reduction of CO₂ to CO. The CO Faraday efficiency reaches 98% at -0.4 V vs. reversible hydrogen electrode, and the FE stays stable from -0.4 to -0.9 V during the 100 h electrolysis time period. This FeN/Fe₃N synergy arises from electron transfer from Fe₃N to FeN and the preferred CO₂ adsorption and reduction to *COOH on FeN. Our study demonstrates a reliable interface control strategy to improve catalytic efficiency of the Fe-N structure for CO₂RR.