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.