Amorphous Copper-Coated Crystalline Cobalt Nanowire for Electrocatalytic Nitrate Reduction to Ammonia in Neutral Medium

Abstract

The direct electrocatalytic reduction of nitrate (NO3−) to ammonia (NH3) presents an energy-efficient and promising strategy for wastewater treatment and the nitrogen cycle. However, under neutral conditions, the electrocatalytic process faces the challenge of insufficient active hydrogen (*H) supply and difficulty in hydrogenation of nitrogen-containing intermediates. Herein, in this work, an amorphous copper-coated crystalline cobalt nanowire (c-Co@a-Cu) catalyst is successfully fabricated for nitrate electroreduction, which achieves a high NH3 yield rate (4.63 mg h−1 cm−2) and Faradaic efficiency (99.6%) at −0.6 V versus RHE in a neutral medium, outperforming its crystalline counterpart. The high-resolution HAADF-STEM and theoretical calculations indicate that amorphous Cu species coating on the Co nanowire surface synergistically enhance NO₃⁻ adsorption via Co-Cu interactions. The c-Co@a-Cu catalyst lowers the energy barrier for *NO3H formation from *NO3, suppresses the hydrogen evolution reaction (HER), and provides abundant reactive hydrogen (*H) to facilitate hydrogenation of nitrogenous intermediates, ultimately accelerating nitrate-to-ammonia conversion. Furthermore, a peak power density up to 5.90 mW cm−2 and an NH3 yield of 277.20 µg h−1 cm−2 have been realized in a homemade Zn-NO3-battery, achieving the integration of power output, nitrate treatment, and green ammonia production.