Electrochemical performance evaluation of template-assisted and morphology-modified ultra-small-sized NiO as electrodes for supercapacitors

Nickel oxide is a significant candidate for the supercapacitor electrode application due to its high theoretical capacitance. This work demonstrates the synthesis of ultra-small-sized NiO nanomaterial using Polyvinyl alcohol template-assisted hydrothermal route succeeded by a significant annealing process. The crystallinity, chemical state, and bonding properties of the NiO materials are evaluated by X-ray diffraction studies, X-ray photoelectron, Raman, and Fourier transform infrared spectroscopic analyses. The morphological features are controlled by a variation of PVA template, and the high concentrations of PVA template provide ultra-small-sized NiO nanomaterial. The surface morphological features are characterized using scanning electron microscopy and high-resolution transmission electron microscopy. The pseudocapacitor behavior of NiO materials was confirmed by the electrochemical performance studies using cyclic voltammetry, EIS, and galvanocharge-discharge measurements. The ultra-small-sized NiO material possessed a specific capacitance of 534.5 Cg(-1) and good rate capability at a scan rate of 5 mVs(-1). The discharge curve provides the specific capacitance of 563.75 Cg(-1) at a current density of 1 Ag-1 and at a scan rate of 100 mVs(-1), withstands 91% of its primary capacitance after 2000 cycles. This work authenticates an efficient approach for enhancing the potential of metal oxides for energy storage applications.