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 (NO). 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 NO, thus promoting the electrochemical reduction of NO. Therefore, the as-prepared electrode exhibited enhanced electrocatalytic activity for NO reduction. The composite electrode with the Cu/Fe molar ratio of 1:2 achieved the highest NO removal (79.4 %) and the lowest energy consumption (0.0023 kW h mg). Furthermore, the composite electrode had a robust NO removal capacity under various conditions. Benefitting from the electrochlorination on the anode, this electrochemical system achieved nitrogen (N) 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.