Supercapacitors (SC) represent a superior storage system as they exhibit higher specific capacitance, higher power density, faster charge/discharge time, and longer charge/discharge cycle lifes. Specifically, hybrid SC comprising both electric double layer capacitors and pseudo-capacitive materials have received attention due to better energy storage capacity. Cobalt oxide (Co3O4), in particular, has received much research attention as pseudocapacitive material due to its favorable capacitive characteristics and environmentally friendliness. Binary nanocomposite materials comprised of Co3O4 nanocrystals embedded in reduced graphene oxide (RGO) sheet were synthesized using one-pot hydrothermal synthetic route without using any structure guiding surfactant. A 1/8 corner of a cubic shape Co3O4 crystal was observed under TEM. Shape and size of Co3O4 crystals varied from particle-type, octahedral, and aggregates of particles, with increase in concentration of Co3O4 in the Co3O4/RGO composite. Cyclic voltammetry and charge/discharge measurements in aqueous KOH electrolyte revealed that the Co3O4/RGO composite material exhibits electrochemical supercapacitive performance giving specific capacitance of 487 F/ at scan rate of 5 mV/s along with outstanding cyclic stability sustaining 96.6% of capacitance after 2000 cycles.
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