Carbon‐Bonded Fe ₃ C‐Based Electrocatalysts Derived from Metal‐Coordination Polymers for Efficient Nitrate Reduction to Ammonia

ABSTRACT Electrochemical reduction of nitrate (NO ₃ ⁻ ) offers a sustainable route for synthesizing ammonia (NH ₃ ) and thus balancing the nitrogen cycle. Metallic Fe has been dominantly explored as a low‐cost and efficient catalysts for this process, which, however, suffers from intrinsically poor stability due to severe corrosion. Herein, we report the effective development of Fe ₃ C‐based nanoparticles for electrochemical NH ₃ synthesis, which features the strong bonding with carbon layers by controllable pyrolysis of an Fe‐based coordination polymer (FeCP). It is revealed that the Fe ₃ C is partially transformed into Fe ₃ O ₄ during the reaction, while the remaining Fe ₃ C is still chemically bonded with carbon layers through Fe─C bonds. The generated heterogeneous catalyst possesses optimized electronic structure, effectively facilitating the NO ₃ ⁻ adsorption and subsequent protonation. Simultaneously, the Fe─C bonding interface is beneficial for suppressing the Fe leaching during the long‐term testing, overcoming the intrinsic issue of Fe‐based catalysts. The as‐obtained catalyst shows a high Faradaic efficiency of 92.6% at −0.6 V (versus reversible hydrogen electrode, vs. RHE) and a high NH ₃ yield rate of 17.7 mg h ⁻¹ mg ⁻¹ _cat ., together with the stable operation within 96 h at −1.0 V vs. RHE. This study provides a facile strategy toward stabilizing iron‐based electrocatalysts for cost‐effective and sustainable NH ₃ production.