Preparation and electrochemical performance of NiCo2O4@NiCo2O4 composite nanoplates for high performance supercapacitor applications

Abstract

Currently, enormous attention is being paid to the difficult design and synthesis of hierarchical nanosheet structures for high-performance supercapacitors. In the present study, we have explored electrochemically synthesized nanostructures of free standing NiCo₂O₄@NiCo₂O₄ composite electrode interconnected hierarchical nanoplates, and NiCo₂O₄ connected hierarchical nanowires were directly grown on a high conductivity Ni foam substrate as an electrode for supercapacitor applications through a cost effective and simple chemical bath deposition method. The electrochemical properties were investigated via cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy studies. This optimized NiCo₂O₄@NiCo₂O₄ nanoplate electrode delivered a remarkable specific capacitance of 2800 F g⁻¹ at a current density of 35 A g⁻¹, which is higher than that of the NiCo₂O₄ nanowire electrode (1200 F g⁻¹ at 35 A g⁻¹) in 3 M KOH aqueous solution, with good electrochemical and superior cycling life properties because of its higher conductivity, broad surface area and the mesopores on its walls. The NiCo₂O₄@NiCo₂O₄ nanoplate composite electrode is directly grown on the high conductivity Ni foam substrate with NiCo₂O₄ nanowires to support efficient electrocatalytic oxidation reactions. The mesoporous features of the NiCo₂O₄@NiCo₂O₄ nanoplate electrode enhance the properties through fast electron/ion transfer and enhance the utilization of the electrode material and large number of electroactive sites. All these results indicate that the NiCo₂O₄@NiCo₂O₄ nanoplate composite electrode would be a promising positive electrode material for flexible electrochemical capacitors.