Cobalt Oxide/Reduced Graphene Oxide Composite with Enhanced Electrochemical Supercapacitance Performance

Binary nanocomposite materials comprised of cobalt oxide (Co3O4) nanocrystals embedded in reduced graphene oxide (RGO) sheet were fabricated using one-pot hydrothermal synthetic route without using any structure guiding surfactant. We succeeded to visualize a 1/8 corner of a single cubic shape Co3O4 crystal under transmission electron microscopy (TEM). Shape and size of Co3O4 crystals varies from particle-type (size similar to 10 nm), octahedral (size similar to 20 nm) and aggregates of particles (size in the range of 50-80 nm) with increase in concentration of Co3O4 in the Co3O4/RGO composite. Cyclic voltammetry and charge/discharge measurements in aqueous KOH electrolyte (2 M) revealed that the Co3O4/RGO composite material exhibits electrochemical supercapacitive performance giving specific capacitance of 487 F g(-1) at scan rate of 5mVs(-1) followed by outstanding cyclic stability sustaining 96.6% of capacitance after 2000 cycles.