Evidence for Oxygen Reduction Reaction Activity of a Ni(OH)2/Graphene Oxide Catalyst
A Ni(OH)2/graphene oxide material was synthesized using a single step microwave reduction method. Cyclic voltammetry shows that the Ni(OH)2/graphene oxide material has a peak potential of -310 mV vs. Ag/AgCl, a shift of + 110 mV as compared to the unsupported Ni(OH)2 nanoparticles and + 90 mV as compared to the graphene oxide support alone. Rotating disk electrode studies confirm that the activity of the Ni(OH)2/graphene oxide catalyst is greater than either the graphene oxide support or the Ni(OH)2 nanoparticles alone. Significantly, the limiting current density of the oxygen reduction reaction on the Ni(OH)2/graphene oxide catalyst is 1.3 mA/cm2 (as normalized by electrochemically active surface area) and the electron transfer number is 3.5. Chronoamperometry demonstrates that the Ni(OH)2/graphene oxide material is relatively stable, with the oxygen reduction current density sustaining a steady state value of 60 % of its initial value. Electrochemical impedance spectroscopy shows that the charge transfer resistance of the Ni(OH)2/graphene oxide catalyst is lower than either the Ni(OH)2 nanoparticles or the graphene oxide support. Taken together, these data indicate that the Ni(OH)2/graphene oxide catalyst exhibits significant oxygen reduction reaction activity which may be related to the interaction of the support and the nanoparticles.