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 degrees 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.