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 (NO3RR) 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 NO3RR. Herein, a tactic is reported to raise rate of NO3RR and increase selectivity to N2 using bimetal catalyst: Co is inclined to act on the key steps needed in NO3RR process, rate‐determining step (RDS: *NO3 to *NO2, 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 N2) 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 NO3RR and offers avenues for designing Fe‐based catalysts to realize the nitrogen‐neutral cycle.

Effects of Ionic Interferents on Electrocatalytic Nitrate Reduction: Mechanistic Insight

“…90,332,333 Reconstruction of the electronic structure during electroreduction can also tailor the catalyst surface to enhance the adsorption of intermediates through the interaction with co-existing ions. 121,334,335 Developing electrodes with optimal cation-induced electric fields for the stabilization of intermediates and the dissociation of water molecules within the EDL would be of great interest. 270,281 Furthermore, given the improved selectivity for NH 3 , albeit often accompanied by an undesired increase in the HER activity, electrodes characterized by an optimal HBE are deemed ideal.…”

“…For example, one of the primary design goals can be the enhancement of adsorption affinity for NO 3 – over ionic impurities in IHP. These features could be achieved by developing materials with tandem catalytic functions, abundant oxygen vacancies or defects, or a positively charged surface via surface coatings. ,, Reconstruction of the electronic structure during electroreduction can also tailor the catalyst surface to enhance the adsorption of intermediates through the interaction with co-existing ions. ,, Developing electrodes with optimal cation-induced electric fields for the stabilization of intermediates and the dissociation of water molecules within the EDL would be of great interest. , Furthermore, given the improved selectivity for NH 3 , albeit often accompanied by an undesired increase in the HER activity, electrodes characterized by an optimal HBE are deemed ideal. , Adjusting catalytic materials to limit HER by minimizing exposure of reactive H* adsorption sites is feasible. Achieving this may involve diminishing the prevalence of surface-terminated OH* and O* groups, which function as active sites for the HER through the facilitation of hydrogen bond formation .…”