Tuning Nitrogen Configurations in Nitrogen-Doped Graphene Encapsulating Fe3C Nanoparticles for Enhanced Nitrate Electroreduction

Electrochemical nitrate reduction reaction (NO3RR) offers a promising technology for the synthesis of ammonia (NH3) and removal of nitrate in wastewater. Herin, we fabricate a series of Fe3C nanoparticles in controllable pyridinic-N doped graphene (Fe3C@NG-X) by a self-sacrificing template method for the NO3RR. Fe3C@NG-10 exhibits high catalytic performance with a Faradaic efficiency (FE) of 94.03 % toward NH3 production at -0.5 V vs. Reversible hydrogen electrode (RHE) and an NH3 yield rate of 477.73 mmol h-1 gcat-1. Additionally, the catalyst also has a FE above 90 % across a broad potential range and NO3- concentration range (12.5-500 mM). During the electrocatalytic process, the material experienced structural reconstruction, forming Fe/Fe3C@NG-X heterojunction. Experimental investigations demonstrate that the remarkable electrocatalytic activity is attributed to the high proportion of pyridinic-N content, and the reconstruction further enhances the overall reduction process.