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) mg(cat)(-1) yield at -1.7 V vs. Hg/HgO. In addition, it also exhibits good long-term stability. N-15 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).

Automated summary

The electrochemical reduction of nitrate (NO3-) to ammonia (NH3) has been successfully achieved using a heterostructured Co/Co3O4 electrocatalyst anchored on N-doped carbon nanotubes. The catalyst exhibits high selectivity and efficiency, with a faradaic efficiency of up to 67% and a yield of 8.319 mg h(-1) mg(cat)(-1). Additionally, it shows excellent long-term stability. Isotopic labelling experiments confirm that the produced NH3 originates from NO3- species. In situ electrochemical Raman spectra provide insights into the stable structure of the catalyst and identify possible intermediates during the electrocatalytic NO3- reduction reaction (NO3RR).