Modulation of hydrogen transfer behaviors over Fe/Cu interfacial sites for a boosted electrocatalytic nitrate reduction reaction

Abstract

An electrocatalytic nitrate reduction reaction (NO₃RR) over Cu-based catalysts represents an energetically feasible route for treating nitrogenous wastewater. However, its efficiency remains limited by the sluggish dissociation of H₂O, which fails to supply active hydrogen (*H) in time to support the hydrogenation of nitrogenous intermediates. Herein, an in situ electrochemical reconstruction strategy is employed to fabricate FeCu-hydroxide nanoarrays directly on copper foam (R-FeCu-OH/CF NAs); owing to the superior hydrogen transfer ability from Fe sites to Cu sites, the synergistic catalytic process (*NO₃ adsorption, *NO₃–*NO₂ and *NO₂ hydrogenation) exhibits favorable thermodynamics. Spectroscopic and theoretical evidence indicates that Fe sites at Fe/Cu interfaces facilitate H₂O dissociation, enabling efficient *H transfer to Cu. This process suppresses NO₂⁻ accumulation and *H coupling, leading to lower energy barriers for NO₃⁻ adsorption and *NO₂/*NO to *NOH. The catalyst achieves up to 92% NO₃⁻ conversion and nearly 100% N₂ selectivity, while providing a stability of up to 60 cycles and a retention of 98%. When deployed as the cathode in a Zn–NO₃⁻ battery, the catalyst delivers an open-circuit voltage of 1.27 V and a peak power density of 9.26 mW cm⁻², outperforming previously reported electrocatalysts. This work elucidates hydrogen-transfer mechanisms and guides the design of efficient electrohydrogenation reactions.