Copper–Nickel Bimetallic-Doped Nanospinel for Efficient Electrochemical Reduction of NO to NH3

Electrocatalytic reduction of nitric oxide (eNORR) represents a promising and sustainable resource strategy. The process is effective at both mitigating anthropogenic air pollution and producing ammonia (NH3) in a manner that is environmentally sustainable and reliant on renewable energy sources. In this study, a series of Cu, Ni metal A-site doped nanospinel composites CuxNi1–xCo2O4 (x = 0, 0.5, 0.9, 1) were synthesized as highly efficient electrocatalysts for NO reduction. The experimental results on catalytic activity showed that Cu0.5Ni0.5Co2O4 exhibited a maximum Faraday efficiency (FE) of 92.73% at −0.9 V vs reversible hydrogen electrode (vs RHE), with NH3 production rate of 99.12 mmol g–1 h–1 at room temperature. Microscopic characterization indicated that the distinctive nanorod structure effectively increased the surface area, promoted electron/ion transport, and exposed more active sites. X-ray photoelectron spectroscopy (XPS) results demonstrated that the interaction between the A-site metals could enhance charge transfer and inhibit the hydrogen evolution reaction (HER). The theoretical analysis comprehensively demonstrated that the enhanced catalytic efficiency of Cu0.5Ni0.5Co2O4 was primarily attributed to the incorporation of Cu metal doping, which facilitated a modification in the electronic structure of NiCo2O4. Furthermore, the synergistic effect between Cu and Ni metal sites significantly facilitated the stable adsorption of the reaction intermediate *NHO on the catalyst surface. This work offers a theoretical guidance that facilitates the efficient and environmentally friendly synthesis of NH3 and the design of spinel catalysts exhibiting superior performance.