Electrocatalytic performance of cobalt/nickel nanoparticles encapsulated by N-doped carbon nanotubes toward the oxygen reduction reaction

Electrocatalysts based on nanosized cobalt or nickel particles encapsulated by nitrogen-doped carbon nanotubes (M@NCNTs (M = Co or Ni)) were synthesized using the calcination method. They were served as the catalyst toward an oxygen reduction reaction (ORR). The results implied that the M@NCNT electrocatalysts had ORR catalytic activity in an alkaline electrolyte. The half-wave potential (E1/2) on the Co@NCNT catalyst reached 0.881 V, which was higher than for commercial Pt/C (0.856 V). The M@NCNT electrocatalysts exhibited good stability in the ORR. After 3000 cycles, the E1/2 for the Co@NCNTs was almost completely unchanged, whereas for the Ni@NCNTs, shifted negatively to 19 mV, was less than for commercial Pt/C (34 mV). These promising electrochemical properties were due to abundant active carbon sites and the synergistic reaction between Co/Ni and NCNTs. Density functional theory calculations indicated that the OOH had strong absorption on the C atoms (adjacent to pyridinic N) in the Co@NCNT and Ni@NCNT catalysts.

Automated summary

Electrocatalysts based on nanosized cobalt or nickel particles encapsulated by nitrogen-doped carbon nanotubes (M@NCNTs (M = Co or Ni)) were synthesized and showed excellent catalytic activity towards oxygen reduction reaction (ORR) in an alkaline electrolyte. The Co@NCNT catalyst had a higher half-wave potential (E1/2) of 0.881 V compared to commercial Pt/C (0.856 V), and both Co@NCNT and Ni@NCNT catalysts exhibited good stability in ORR. Density functional theory calculations revealed strong OOH absorption on the C atoms adjacent to pyridinic N in the Co@NCNT and Ni@NCNT catalysts.