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

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 (Csp) from galvanostatic charge/discharge experiments is higher in all the electrodes in KOH than in NaOH. Co3O4/B-rGO shows the highest Csp 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.