Abstract
In this article, we have synthesized carbon-coated cobalt oxide nanoparticles (NPs) and their nanocomposite with reduced graphene oxide (C@Co3O4/r-GO) via chemical and ultrasonication techniques. The observed higher electrical conductivity (1.4 x 10(-3) S/m) of the nanocomposite than the pristine NPs (1.9 x 10(-8) S/m) was due to the combined effect of the carbon-coating and r-GO nanosheets. The higher specific surface area (118 m(2)/g) of the nanocomposite was due to the relived agglomeration of the NPs via the carbon-coating and r-GO matrix. The nanocomposite based electrode shows exceptional gravimetric capacitance of 674 F/g at 1 A/g and loses just 18% of its initial capacitance after 10(3) charges/discharge cycles. The superior electrochemical performance of the nanocomposite was due to its higher surface area and synergistic improvements between carbon-coated NPs and highly conducive r-GO nanosheets. In the nanocomposite, the r-GO nanosheets play a double role to increase the energy storage properties. For example, the r-GO sheets acted as a capacitive supplement as well as a conducive matrix for a speedy redox reaction. Highly conducive nanocomposite also showed lower charge transfer resistance (Rct similar to 12.78 Omega) during the electrochemical impedance spectroscopic (EIS) tests that further facilitated the redox reaction to achieve higher pseudocapacitance. The observed electrical and electrochemical results demonstrate the potential of the C@Co3O4/r-GO nanocomposite for hybrid supercapacitors.