Graphitic Carbon-NiCo Nanostructures as Efficient Non-Precious-Metal Electrocatalysts for the Oxygen Reduction Reaction

Composites of graphitic carbon layers and transition metals or metal alloys have received considerable attention for use as non-precious-metal catalysts for ecofriendly energy devices. In this paper, we report graphitic carbon-supported NiCo alloys (NiCo@GC) that function as non-precious-metal electrocatalysts for the oxygen reduction reaction under alkaline conditions. In particular, we examined the effect of the pyrolysis temperature on the oxygen reduction activity. The catalyst prepared at 600 °C provided an oxygen reduction half-wave potential (E_1/2) of 0.81 V – only 10 mV less than that of a commercial Pt/C catalyst (0.82 V) – with the transfer of almost four electrons. Structural and chemical studies indicated that the excellent activity and stability of the NiCo@GC catalysts resulted from the strong interactions between (and the combined effects of) the metal and the carbon, dictated by the annealing temperature.