Electrochemical Behavior of Cobalt Oxide/Boron-Incorporated Reduced Graphene Oxide Nanocomposite Electrode for Supercapacitor Applications

Abstract

Electrodes from hydrothermally synthesized boron-incorporated reduced graphene oxide (B-rGO), Co3O4, and Co3O4/B-rGO nanocomposites are tested in 2 M KOH and NaOH electrolytes for supercapacitor applications. Structural characterization was done by x-ray diffraction and x-ray photoelectron spectroscopy. Cyclic voltammogram of B-rGO indicates partial electrical double-layer capacitance and pseudocapacitive behaviors. Co3O4, shows two reversible redox peaks, indicating diffusion-controlled (battery-like) process. Interestingly, Co3O4/B-rGO possesses both the pseudocapacitive and diffusion-controlled features. The specific capacitance (C-sp) from galvanostatic charge/discharge experiments is higher in all the electrodes in KOH than in NaOH. Co3O4/B-rGO shows the highestC(sp)of 600 F g(-1)(270 C g(-1)) at 0.1 A g(-1)and 454 F g(-1)(204 C g(-1)) at 10 A g(-1)in KOH. Co3O4/B-rGO-KOH system retains 87.8% capacitance after 2000 cycles, demonstrating very good cyclic stability. Co3O4/B-rGO-KOH system yields, a remarkable, maximum power density of 2250 W kg(-1)with an energy density of 12.77 W h kg(-1)at 10 A g(-1). The better performance in KOH is attributed to the low hydration sphere radius, high ionic conductivity of K+, low diffusive and charge transfer and electrode resistance, estimated from electrochemical impedance spectroscopy. The electrode-electrolyte combination is crucial for the overall performance as a supercapacitor electrode.