High performance super-capacitive behaviour of deposited manganese oxide/nickel oxide binary electrode system

The chrono-potentiometry technique was used to deposit MnO2-NiO binary metal oxide film on a stainless steel substrate at room temperature. During the electrodeposition process, the concentration of nickel acetate is varied in the fixed 0.01 M manganese acetate solution. The products were characterised by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) and field emission scanning electron microscopy (FESEM). Their capacitive behaviour was studied by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy in two different alkaline electrolytes using a three electrode set-up. The MnO2-NiO binary metal oxide electrode deposited from Ni(CH3COO)2.4H2O:Mn(CH3COO)2.4H2O at a molar ratio of 0.25:0.01 (molar:molar) was found to be the best electrode with the lowest transfer resistance based on the Nyquist plots. The specific capacitance of the best electrode, NiO-25, exhibited a specific capacitance of 435 Fg−1 and 681 Fg−1 with an energy density of 242 Whkg−1 and 213 Whkg−1 in 0.5 M Na2SO4 and 0.5 M KOH electrolyte, respectively.