Defect-Driven Bimetallic Modulation: Accelerating Electrocatalytic Ammonia Oxidation Kinetics via a Nitrogen-Deficient FeCuN-Derived Architecture

Abstract Electrocatalytic ammonia oxidation (AOR) offers an energy-efficient route to carbon-free hydrogen production but is constrained by sluggish multielectron-transfer kinetics and adsorbate evolution mechanism (AEM) scaling relationships. Here, electrodeposition yielded a nickel-foam-supported bimetallic FeCuN catalyst (FeCuN-BH), followed by high-temperature hydrogenation to introduce abundant lattice nitrogen vacancies (FeCuN-AH). The rationally engineered FeCuN-AH architecture demonstrates superior AOR performance, requiring an exceptionally low applied potential of 0.61 V vs the saturated calomel electrode (SCE) to reach 50 mA cm–2, together with an apparent Tafel slope of 934.7 mV dec–1, substantially lower than the 2408 mV dec–1 measured for FeCuN-BH, and stable operation over 50 h. Comprehensive density functional theory (DFT) calculations elucidate a lattice nitrogen vacancy-mediated dual-site synergistic mechanism (LNVM-MSM). The incorporated nitrogen vacancies not only serve as preferential active centers for ammonia adsorption but also drastically reduce the kinetic energy barrier of the rate-determining step (RDS, *NH2 to *NH) from 2.04 eV on pristine copper sites down to 0.90 eV. Furthermore, these defect sites induce local electronic redistribution and modify intermediate adsorption energetics. By circumventing conventional scaling limitations, this defect-driven dual-site structure provides a robust and scalable framework for designing active, durable electrocatalysts for sustainable hydrogen extraction and advanced energy-conversion devices.