Effect of annealing temperature on oxygen reduction reaction of reduced graphene oxide incorporated cobalt oxide nanocomposites for fuel cell applications

Reduced graphene oxide incorporated cobalt oxide nanocomposites were prepared by a simple hydrothermal route followed by annealing the product at 300 °C, 400 °C and 500 °C in air. Structural analysis by X-ray diffraction confirmed the formation of rGO presence and Co3O4 spinel structure. Scanning electron microscopic images of as-synthesized product showed layered reduced graphene oxide structure and the annealed samples showed agglomerated nanoparticles to porous structure. Functional group analysis confirmed the formation of Co3O4 phase and reduced Graphene oxide. The surface area was increased from 13.72 m2/g, to 23.16 m2/g for the sample annealed at 300 °C-500 °C. Electrochemical properties of annealed products were investigated by cyclic voltametry and Rotating Disc Electrode (RDE) measurements produced Oxygen Reduction Reaction (ORR) catalytic activity with 3.2 electron transfer number. The observed onset potential is +0.76 V vs RHE and current density of 3.25 mA/cm2 at 1600 rpm for the sample annealed at 500 °C.