Efficient electrocatalytic nitrate reduction to ammonia at low voltage through copper and graphene oxide co-modified nickel foam

Abstract

Efficient electrocatalytic nitrate (NO₃⁻) reduction reaction (NO₃RR) to valuable ammonia (NH₃) in industrial and domestic wastewater represents a sustainable remediation strategy. However, its implementation under alkaline conditions is impeded by the thermodynamic limitations of the NO₃RR process, as water electrolysis is typically performed at high voltage to activate proton hydrogen (∗H), thereby enabling selective NH₃ production. Herein, we employ copper (Cu) and graphene oxide (GO) to co-modified nickel foam (Cu-GO@NF) by a low-temperature calcination method, which achieves high Faradaic efficiency (99.51 %) and NH₃ selectivity (95.03 %) at such a low voltage (−0.13 V vs. reversible hydrogen electrode), effectively addressing this alkaline dilemma. The synergistic effect of strong NO₃⁻ adsorption activity by Cu and high electrolytic water dissociation ability to release ∗H by nickel (Ni) not only enhances the catalytic performance but also accelerates electron transfer, thus achieving a low reduction potential. Meanwhile, the hydrated cation–π interactions between GO and metal Cu and Ni provide protection to the Cu-GO@NF catalyst that shows excellent stability during the continuous 150 h reaction, the Cu and Ni contents decrease by only 3.3 % and 4.5 % after stability test. Furthermore, mechanistic studies reveal the NO₃RR pathway, contributing to optimization and development of subsequent catalysts.