Synergistic regulation of intermediate conversion and activated hydrogen supply on Fe–Ru diatomic sites drives efficient electroreduction of neutral nitrate to ammonia

Abstract

Electrochemical conversion of nitrate (NO₃⁻) represents an efficient strategy for mitigating NO₃⁻ pollutants while offering a promising alternative route for sustainable ammonia (NH₃) synthesis. However, this process is hindered by a kinetic mismatch among initial NO₃⁻ adsorption, active hydrogen (*H) formation via water dissociation, and subsequent stepwise hydrogenation. Herein, an Fe–Ru diatomic catalyst (FeRuSA NC) was designed and synthesized, and it delivers a remarkable NH₃ yield rate of 1.99 mmol h⁻¹ mg_cat.⁻¹ and a high faradaic efficiency (FE) of 96.8% at −1.2 V vs. RHE. The Fe–Ru diatomic sites reduce the energy barriers for the initial adsorption and the subsequent rate-determining hydrogenation step, thereby facilitating the reduction of NO₃⁻ to NO₂⁻ and subsequent hydrogenation to NH₃. Moreover, the Fe–Ru diatomic sites promote water dissociation via modulating the interfacial water structure (enriched K-H₂O interactions) and suppress the HER, thus supplying sufficient *H for the deep hydrogenation of nitrogenous intermediates. This work unveils interactions between diatomic sites and multiple reactants/intermediates, providing new insights into the rational design of atomically dispersed catalysts for efficient NO₃⁻ reduction and NH₃ synthesis.