Ru‐Doped Cu‐Cu ₂ O Heterojunction on Iron Foam for Efficient Electrochemical Removal of Nitrate

ABSTRACT Electrochemical nitrate reduction diminishes nitrate (NO ₃ ⁻ ) levels in effluent by controlling product selectivity through catalyst engineering. Nonetheless, attaining high N ₂ selectivity continues to be challenging owing to competing reaction mechanisms and the generation of byproducts. In this study, a highly selective reduction of NO ₃ ⁻ to N ₂ was accomplished through the in situ growth of a ruthenium‐doped Cu‐Cu ₂ O heterostructure on an iron foam substrate (Ru/Cu‐Cu ₂ O@IF). The three‐dimensional interconnected pores of IF substantially enhance the density of active sites, while the incorporation of Ru adjusts the electronic structure of Cu sites and refines the reaction pathway. The synergistic interaction between Ru and Cu facilitates sequential deoxygenation and hydrogenation of nitrate, enhancing the efficacy of electron utilisation. Under optimal conditions, Ru/Cu‐Cu ₂ O@IF attains a 98.9% removal rate of NO ₃ ⁻ ‐N and approaches 100% N ₂ selectivity within 6 h. Furthermore, the as‐prepared heterojunction electrocatalyst demonstrates a removal efficacy exceeding 90% across a broad pH range (3–11) and at initial nitrate concentrations (25–100 mg/L). These findings indicate that the material remains stable and adaptable, with no notable decrease in performance observed after eight cycles. Overall, this study presents a design approach for investigating foam metal supports and multi‐element metal systems in electrocatalytic materials.