Nickel Oxide Accelerated Iron Nanostructures for Electrocatalytic Nitrate Reduction to Ammonia

Rapid industrial growth has led to increasing nitrate (NO3–) wastewater discharge, disrupting ecosystems and threatening human health. Electrocatalytic NO3–-to-NH3 (NITRR) offers a promising method to solve environmental problems and provide clean energy. Electrocatalytic NITRR involves multielectron transfer and hydrogenation processes, in which the hydrogenation of *NO is crucial to the whole reaction. However, the hydrogenation process of *NO is sluggish due to the high chemical dissociation energy of the N–O bond. Here, the Fe nanoplates and nickel oxide/nickel-foam composite material (Fe@NiO/NF) was fabricated and demonstrated an excellent NITRR performance with a high faradaic efficiency over 98.7% at −0.45 V (vs RHE). More importantly, the Fe@NiO/NF electrode maintained excellent stability over 100 h. The condition experiments and electron spin resonance demonstrated that the synergistic interaction between Fe nanoplates and NiO significantly promoted the formation of hydrogen radicals (*H) on Fe@NiO/NF. Furthermore, density functional theory calculations revealed that this synergy effectively lowers the energy barrier for the hydrogenation of the *NO intermediate on Fe@NiO/NF, thereby accelerating the overall hydrogenation process. This study proposes a cost-effective and efficient method for treating NO3– wastewater while recovering valuable nitrogen resources.