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 µg·h−1·cm−2 and Faradaic efficiency of 99.83