Characterization of nanostructured nickel cobalt oxide-polyvinyl alcohol composite films for supercapacitor application

Abstract

In the present work, thin films of nickel cobalt oxide and polyvinyl alcohol nanocomposite (NCO-PVA) are prepared by chemical methods. The as-prepared NCO-PVA films have been structurally studied by X-ray diffraction and Fourier transform infrared spectroscopy. The morphology of the NCO-PVA films has been studied by Field emission scanning electron microscopy and High-resolution transmission electron microscopy. X-ray diffraction analysis has been used to study its crystallinity and phase. The optical properties of NCO-PVA nanocomposite films have also been studied. The surface area and pore size measurements have also been done. The UV-Vis spectrum analysis reveals that the films possess two direct band gaps (2.91 eV and 3.48 eV). The red shift of Photoluminescence emission has been observed for nanocomposite films with increasing excitation intensity. The AC electrical conductivity of NCO-PVA films has been studied as the high value of AC conductivity is essential for getting high power and high energy density in supercapacitors. Also, the high value of the dielectric constant of nanocomposite at small frequencies shows its supercapacitive nature. A short relaxation time (~6.37 ≤ 10−7 s) reveals a very small delay in molecular polarization along with changing the electric field, suggesting fewer energy losses. Electrochemical performance is checked by cyclic voltammetry, galvanostatic charge-discharge, and impedance spectroscopy measurements using 1 M Na2SO4neutral aqueous electrolytic solution. Also, the symmetric supercapacitor has been fabricated, using NCO-PVA films as the electrodes, which exhibits the specific capacitance value of50 F g−1and energy density of 18.9 W h kg−1. The results reveal that the prepared nanocomposite films have enough potential for supercapacitor device fabrication, especially the flexible supercapacitors.