Abstract. 20 nm sized Co3O4 nanoparticles are in-situ grown on the chemically reduced graphene oxide (rGO) sheets to form a rGO-Co3O4 composite during hydrothermal processing. The rGO-Co3O4 composite is employed as the pseudocapacitor electrode in the 2 M KOH aqueous electrolyte solution. The rGOeCo3O4 composite electrode exhibits a specific capacitance of 472 F g-1 at a scan rate of 2mV s…