Electrocatalytic nitrate-to-ammonia conversion on CoO/CuO nanoarrays using Zn-nitrate batteries

Zn-NO₃^- batteries can generate electricity while producing NH₃ in an environmentally friendly manner, making them a very promising device. However, the conversion of NO₃^- to NH₃ involves a proton-assisted 8-electron (8e^-) transfer process with a high kinetic barrier, requiring high-performance catalysts to realize the potential applications of this technology. Herein, we propose a heterostructured CoO/CuO nanoarray electrocatalyst prepared on a copper foam (CoO/CuO-NA/CF) that can electrocatalytically and efficiently convert NO₃^- to NH₃ at low potential and achieves a maximum NH₃ yield of 296.9 μmol h^-1 cm^-2 and the Faraday efficiency (FE) of 92.9% at the -0.2 V vs. reversible hydrogen electrode (RHE). Impressively, Zn-NO₃^- battery based on the monolithic CoO/CuO-NA/CF electrode delivers a high NH₃ yield of 60.3 μmol h^-1 cm^-2, FE_NH3 of 82.0%, and a power density of 4.3 mW cm^-2. This study provides a paradigm for heterostructured catalyst preparation for the energy-efficient production of NH₃ and simultaneously generating electrical energy.