Denitrification Performance and Mechanism of Nitrogen Doped Carbon Coated Cu–Fe Nanoalloy

Electrochemically converting nitrate into ammonia (ECNA) is expected to achieve wastewater treatment combined with distributed ammonia generation, which is beneficial to restoring the globally disrupted nitrogen cycle. While sluggish reaction kinetics and insufficient selectivity towards ammonia generation greatly hinder the practical application of ECNA. In this study, chloride-derived bimetallic Cu–Fe catalysts with flexible Cu/Fe ratios confined by nitrogen-doped carbon (Cu_xFe_y/CN) were constructed through reactive mechanical milling combined with thermal pyrolysis, enabling stable and efficient nitrate-to-ammonia conversion. The CN coating effectively prevents further oxidation of Fe²⁺, promoting electron transfer from Fe²⁺ to Cu⁺ and maintaining the highly reactive center Cu⁺/Cu stable. The optimized Cu₃Fe/CN_700-15 sample exhibits good nitrate conversion efficiency of 57.0% and ammonium selectivity of 61.6% within 6 h at −0.7 V relative to the reversible hydrogen electrode (vs. RHE). This work provides a new idea for stable and sustainable bimetallic denitrification.