Electrocatalytic reduction of nitrate by carbon encapsulated Cu-Fe electroactive nanocatalysts on Ni foam

Electrocatalytic denitrification is an attractive and effective method for complete elimination of nitrate (NO₃^-). However, its application is limited by the activity and stability of the electrocatalyst. In this work, a novel bimetallic electrode was synthesized, in which N-doped graphitized carbon sealed with Cu and Fe nanoparticles and immobilized them on nickel foam (CuFe NPs@NC/NF) without any chemical binder. The immobilized Cu-Fe nanoparticles not only facilitated the adsorption of the reactant but also enhanced the electron transfer between the cathode and NO₃^-, thus promoting the electrochemical reduction of NO₃^-. Therefore, the as-prepared electrode exhibited enhanced electrocatalytic activity for NO₃^- reduction. The composite electrode with the Cu/Fe molar ratio of 1:2 achieved the highest NO₃^- removal (79.4 %) and the lowest energy consumption (0.0023 kW h mg^-1). Furthermore, the composite electrode had a robust NO₃^- removal capacity under various conditions. Benefitting from the electrochlorination on the anode, this electrochemical system achieved nitrogen (N₂) selectivity of 94.0 %. Moreover, CuFe NPs@NC/NF exhibited good stability after 15 cycles, which should be attributed to the graphitized carbon layer. This study confirmed that CuFe NPs@NC/NF electrode is a promising and inexpensive electrode with long-term stability for electrocatalytic denitrification.