Characterization of nickel cobalt oxide: a potential material for supercapacitor

Hydrothermal synthesis technique is used to synthesize nanosized NiCo2O4 particles. The as-synthesized nanosized particles are structurally characterized by Raman spectroscopy. The nanostructure and morphology of the prepared nanoparticles are studied by Field Effect Scanning Electron Microscopy and Raman spectroscopy. DC electrical conductivity has been measured in the temperature range 303-402 K and the activation energy has been calculated. The absorbance of the nanoparticles in the UV-Visible range is recorded. The absorption spectrum analysis shows that the material possesses two direct band gaps, one corresponding to 1.74 eV and the other corresponding to 2.2 eV. The changes in AC conductivity and dielectric constant with a variation of frequency are studied. The AC conductivity exhibits Jonscher's power law. From the dielectric studies, it is seen that with increasing frequency, the dielectric constant reduces. Also, the dielectric constant value of the nanoparticles is very high which indicates its supercapacitive behaviour. The small dielectric loss (0.32 at 3.5 kHz) shows a very small delay (relaxation time similar to 4.54 x 10(-5)s) in molecular polarization along with the varying electric field which reveals that the energy losses are less. The AC impedance spectroscopy also exhibits that the synthesized material has the potential as a good supercapacitive material.