Flower-Like\nNickel–Cobalt Oxide Decorated Dopamine-Derived\nCarbon Nanocomposite for High Performance Supercapacitor Applications

Abstract

The\nhighly open space flower, coin, peony flower, and leaf-like\nnickel–cobalt oxide nanostructured materials with and without\ndopamine as a carbon source (D_1.5NiCo₂O₄, D_1.0NiCo₂O₄ (D-NiCo₂O₄), D_0.5NiCo₂O₄, and D_0.0NiCo₂O₄ (D- free NiCo₂O₄)) are prepared by a low temperature chemical\nsynthesis method with improved electrical conductivity, providing\nthe longtime electron pathway, and high surface area for high performance\nsupercapacitors. The structure and morphology of the as-synthesized\nsamples were characterized by X-ray diffraction pattern, X-ray photoelectron\nspectroscopy, scanning electron microscope, field emission-transmission\nelectron microscope, and N₂ adsorption–desorption\nisotherms. Electrochemical properties of the electrodes were analyzed\nby cyclic voltammetry and galvanostatic charge–discharge methods.\nNotably, the as-synthesized flower-like D-NiCo₂O₄ nanocomposite exhibited a maximum specific capacitance of 667 F\ng^–1, which is superior to D- free NiCo₂O₄ viz. 202 F g^–1 at 5 A g^–1 with excellent cyclic stability of about 95% and 86% at 10 A g^–1 after 2000 charge–discharge cycles in 2.0\nM KOH aqueous electrolyte solution for D-NiCo₂O₄, and D-free NiCo₂O₄, respectively. In addition,\nan asymmetric supercapacitor device is fabricated through D-NiCo₂O₄ as a positive electrode and biomass-derived\nAC as a negative electrode with the potential range of 0–1.5\nV in PVA-KOH gel electrolyte solution. These results indicate that\nthe as-prepared electrodes have high specific capacitance, excellent\ncycle stability, and good rate capability, which surpass several related\nmetal oxide electrodes.