Efficient fabrication of Cd-doped NiO nanostructures as high-performance electrode materials for supercapacitors

Pure and cadmium-doped NiO nanostructured porous materials, including
various concentrations, were successfully synthesized via a solvothermal
approach consuming citric acid as a hydrolysis-regulating substance and
evaluated for supercapacitor applications. Powder X-ray diffraction was
employed to examine the phase composition of nanomaterials. The typical
crystallite size of the oxide samples ranged from 21 to 9 nm. Fourier transform
infrared spectroscopy established the presence of M–O bonding. Morphological
investigations revealed a mesoporous, flake-like building in the prepared
materials. Energy-dispersive X-ray spectroscopy was used to find out the
oxidation states and elemental composition, respectively. Electrochemical
performance was analyzed in an aqueous electrolyte using cyclic voltammetry,
galvanostatic charge–discharge, and electrochemical impedance spectroscopy.
Among the four electrodes, Cd–nickel-oxide (X = 10%) exhibited the maximum
surface redox activity and brought a superior specific capacitance of 832 F g−1 at
a current density of 1 A g−1