Cu–Fe Synergistic Active Sites Boost Kinetics of Electrochemical Nitrate Reduction

Abstract

Electrochemical conversion of nitrate offers an efficient solution to nitrate pollution and a sustainable strategy for ammonia generation. Cu and Fe bimetallic electrocatalysts exhibit excellent electrochemical reduction of nitrate (NO3RR) reactivity but the conventional preparation strategy is complex and time‐consuming and this reaction is still suffers from unsatisfied kinetic and unidentified mechanisms. Herein, in situ electrodeposition strategy is employed to induce Cu to modify the Fe active sites of iron‐based N‐doping carbon nanofiber electrode (Fe/Fe3C@NCNFs) during NO3RR in Cu‐contained nitrate solution. Benefiting from the synergistic effect between Cu and Fe sites of Cu─Fe/Fe3C@NCNFs electrode, superior activity of rate‐determining reaction (*NO3 to *NO2) and reduced energy barriers of the following deoxidation and hydrogenation steps are achieved. Compared with Fe/Fe3C@NCNFs‐500, the pseudo‐first‐order (PFO) rate constant for NO3RR by Cu─Fe/Fe3C@NCNFs demonstrates nearly two‐fold improvement with high current efficiencies over wide pH and voltage range. Furthermore, the maximum NO3─N removal capacity and N2 selectivity of Cu─Fe/Fe3C@NCNFs reach 15593.8 mg N g−1 Fe and ca. 92% after twenty cycles. This work offers an avenue for highly active bimetallic electrode design, paving more insights into the interactions between active site construction and NO3RR performance.

Tandem catalysis in electrocatalytic nitrate reduction: Unlocking efficiency and mechanism

“…For example, at low nitrate concentrations, the efficiency of nitrate reduction is greatly influenced by the presence of adsorbed ions, whereas at high nitrate concentrations, a larger number of free active sites on the catalysts are required. [74][75][76] The electron reduction pathways begin with the initial adsorption and reduction of nitrate into nitrite, followed by subsequent reductions that contribute to the formation of adsorbed NO (Equations 3-5). Subsequently, the generated NO (ads) can form in the solution and undergo dimer evolution into N 2 O, which ultimately undergoes transformation into nitrogen gas (Equations 6-8).…”