Heterostructured Co/Co3O4 anchored 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 mgcat−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).