Co-deposition of Cu_xFe_yon nickel foam promotes NH₃ desorption to enhance nitrate reduction activity and ammonia selectivity

The metal with highly occupied d-orbitals and unclosed d-orbitals shells (Cu, Pd and Pt) was widely used as catalyst in electrochemical NO₃^- reduction reaction (NO₃^-RR), but the production ammonia adsorped on active sites of surface hinders NO₃^-RR. Herein, a series of Cu_xFe_y electrodes (Cu₇₅Fe₂₅, Cu₅₀Fe₅₀ and Cu₂₅Fe₇₅) were prepared through electrochemical co-deposition of Cu and Fe on nickel foam (NF) as a cathode. The Cu_xFe_y/NF electrodes showed nearly 100 % NO₃^-RR efficiency in 3 h and excellent durability. Meanwhile Cu₇₅Fe₂₅ had high current efficiency (98.01 %) in 30 min and a good stability of nitrate reduction activity after 8 cyclic experiments. The improved electrocatalytic activity on nitrate reduction is attributed to the high electron transfer rate, high adsorption capacity of electroactive species, high electrochemically active surface areas (ECSA) and double layer capacitance (C_dl) of the Cu₇₅Fe₂₅ electrode. Nitrate was first converted to nitrite, followed by acceptance of six-electron to produce NH₃. Density functional theory (DFT) calculations confirmed that the Fe-shifted Cu d-band center contributed to weak adsorption energies of ammonia, and thus resulted in superior activity and selectivity toward NO₃^- reduction to NH₃. Taking together, results showed the promising application of CuxFey/NF electrodes in electrocatalytic denitrification and ammonia production from wastewater. © 2025 Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.