Efficient electrocatalytic reduction of nitrate to ammonia at low concentration by copper-cobalt oxide nanowires with shell-core structure

Electrocatalytic nitrate reduction to ammonia (NO3-RR) for removing nitrate from wastewater is a promising but challengeable technology that is increasingly studied. Herein, we developed an efficient CuOx and CoCuOx composed hybrid catalyst (CoCuOx@CuOx/copper foam (CF)), characteristic of distinctive shell-core nanowires grown on CF substrate with CuOx core and CoCuOx shell. The built-in electric field formed at the interface of the CoO/Cu2O heterostructure promotes NO3- adsorption by modulating the charge distribution at the interface, which greatly improves the ammonia yield rate and Faradaic efficiency. At -0.2 V vs. reversible hydrogen electrode (RHE), CoCuOx@CuOx/CF achieves not only an excellent ammonia yield rate of up to 519.1 mu g.h(-1).cm(-2) and Faradaic efficiency of 99.83% at 1 mM NO3- concentration, but also excellent mechanical stabilities. This study provides a novel pathway to design electrocatalyst for the removal of nitrate from dilute nitric acid solutions (<= 2 mM).