Physicochemical and supercapacitive properties of electroplated nickel oxide electrode: effect of solution molarity

With an aim of physicochemical characteristics and electrochemical supercapacitor studies with X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDAX) technique, X-ray photoelectron spectroscopy (XPS) and surface wettability, nickel oxide (NiO) thin films of different molarities i.e. (0.1, 0.2, 0.3 and 0.4 M) have been synthesized onto stainless-steel substrate using potentiostatic mode of electrochemical method. The XRD result confirms crystalline nature with cubic crystal structure of the NiO. The SEM micrographs reveal homogenous and smooth surfaces. Existence of Ni and O in EDAX spectrums of all samples supports the formation of NiO. Expected peaks are confirmed from XPS surface analyses. Contact angle measurement of 0.1, 0.2 M film showed hydrophilic, however 0.3, 0.4 M film showed hydrophobic in character. The optimal potential for potentiostatic mode of electrochemical method of NiO is 1.8 V. The electrochemical properties of the NiO electrodes are studied in detail by cyclic voltammogram, galvanostatic charge-discharge and electrochemical impedance spectroscopy measurements. The specific capacitance of the NiO electrode is 667.24 Fg(-1) in Na2SO4 electrolyte of 1 mol/L. The achieved specific energy, power and coulombic efficiency of NiO electrode were 2.55 Whkg(-1), 6.23 kWkg(-1) and 92.86% respectively. Moreover, the NiO electrode shows excellent cyclic performance after 1000 cycles. An effective and convenient technique has been developed to produce nickel oxide material promising for designing of innovative capacitors.