Heterostructure engineered construction of N-doped CuO@Co3O4 for highly efficient electrocatalytic reduction of nitrate to ammonia†

The electrochemical reduction of nitrate can be a promising and sustainable alternative for the industrially used, energy-intensive Haber–Bosch process under mild conditions and also solve the issue of nitrate nitrogen pollution in water. We present here the facile construction of an N-doped CuO@Co₃O₄/NF nanoarray on nickel foam for highly efficient NH₃ electrosynthesis via selective NO₃⁻ reduction in neutral electrolyte. At −0.85 V (versus the reversible hydrogen electrode (RHE)), this N-doped CuO@Co₃O₄/NF nanoarray obtained an outstanding Faraday efficiency (FE) of 99.78% and NH₃ yield of up to 31.92 mg h⁻¹ cm⁻² when operated in 0.1 M phosphate buffer solution with added 50 mM NaNO₃. In addition, its excellent electrochemical performance was maintained for at least 12 h. Furthermore, according to the characterization, the enhanced electrocatalytic performance could be attributed to the synergistic effect of N-dopant and relatively large amounts of Co(II) and oxygen vacancies (OVs) in the heterostructure, leading to the suppression of the hydrogen evolution reaction (HER) and the improvement of electron/mass transfer at the N-doped CuO@Co₃O₄/NF heterostructure.