Electronic structure modulation of Ni-decorated Cu nanowire electrode for efficient nitrate-to-ammonia conversion in...

Electrocatalytic nitrate-to-ammonia conversion has emerged as a pivotal green technology that simultaneously enables waste valorization and sustainable ammonia production, offering a promising alternative to the energy-intensive Haber-Bosch process. Herein, we reported a highly efficient Ni-decorated Cu nanowire electrode (Ni-CuNW) that exhibited remarkable electrocatalytic activity under challenging neutral media, which typically suffers from insufficient H* supply and severe competition from the hydrogen evolution reaction (HER). The optimized electrode achieved near complete nitrate removal with 99.5% NH₄⁺-N selectivity and 95.5% Faradaic efficiency (FE) for NH₃ production during treatment of nitrate-laden wastewater (50 mg L^-1 NO₃^--N), and maintained an NH₃ FE of 90% even in high-concentration wastewater containing 2000 mg L^-1 NO₃^--N. An integrated reactor incorporating an in-situ ammonia recovery unit was constructed, and over 95% nitrate removal and 85% NH₃ recovery were achieved under various nitrate concentrations, demonstrating its robust practical applicability. Mechanism studies revealed that the superior performance originated from the incorporation of Ni(OH)₂ species, which modulated the electronic structure of Cu and induced surface electron redistribution. This electronic structure modulation accelerated interfacial electron transfer and strengthened the adsorption of NO₃^- and nitrogen-containing intermediates. Concurrently, Ni species incorporation selectively suppressed the competing HER at active sites, thereby endowing the Ni-CuNW electrode with exceptional FE for NH₃ production. This work presents an efficient and scalable strategy for synthesizing advanced electrocatalysts suitable for both wastewater remediation and sustainable ammonia production.