Heterostructured Co/Co3O4anchored on N-doped carbon nanotubes as a highly efficient electrocatalyst for nitrate reduction to ammonia

The electrochemical reduction of nitrate (NO₃^-) to ammonia (NH₃) has emerged as an attractive approach for selectively reducing NO₃^- to highly value-added NH₃ and removing NO₃^- pollutants simultaneously. In this work, a heterostructured Co/Co₃O₄ electrocatalyst anchored on N-doped carbon nanotubes was prepared and applied for the NO₃^- reduction towards NH₃ under alkaline conditions. The catalyst achieves outstanding performance with up to 67% NH₃ faradaic efficiency at -1.2 V vs. Hg/HgO and 8.319 mg h^-1 mg_cat^-1 yield at -1.7 V vs. Hg/HgO. In addition, it also exhibits good long-term stability. ¹⁵N isotopic labelling experiments prove that the yielded NH₃ is derived from NO₃^- species. In situ electrochemical Raman spectra revealed that the structure of the as-prepared catalyst showed outstanding stability and identified possible intermediates during the electrocatalytic NO₃^- reduction reaction (NO₃RR).