Relay Catalysis of Fe and Co with Multi‐Active Sites for Specialized Division of Labor in Electrocatalytic Nitrate Reduction Reaction

Abstract Electrocatalytic nitrate reduction reaction (NO 3 RR) driven by renewable energy is a promising technology for the removal of nitrate‐containing wastewater. However, the sluggish kinetics resulted from the complex proton‐coupled electron transfer and various intermediates remain the key barriers for large‐scale application of NO 3 RR. Herein, a tactic is reported to raise rate of NO 3 RR and increase selectivity to N 2 using bimetal catalyst: Co is inclined to act on the key steps needed in NO 3 RR process, rate‐determining step (RDS: *NO 3 to *NO 2 , the asterisk means intermediates) and the subsequent *N hydrogenation as well as Fe exhibits the efficient activity for the selectivity‐ determining step (SDS: *NO to *N then to N 2 ) via a relay catalysis mechanism. A removal efficiency of 78.5% and an ultra‐long cycle stability of 60 cycles (12 h per cycle) are achieved on FeCo alloy confined with nitrogen‐doped porous carbon nanofibers (FeCo‐NPCNFs). DFT calculations unveil that the introduction of Co active site not only regulates the d‐band center of FeCo alloy, optimizes the adsorption of intermediates, but also has a strong capacity to supply active hydrogen species. Clearly, this study elucidates the effects of bimetallic relay catalysis on the performance of electrocatalytic NO 3 RR and offers avenues for designing Fe‐based catalysts to realize the nitrogen‐neutral cycle.