Synthesis, Characterization and Electrochemical Properties of Capsule-Like NiO Nanoparticles

Capsule-like NiO nanoparticles were prepared by heat-treatment of the cathodically electrodeposited nickel hydroxide at 300°C for three hours. The hydroxide precursor was deposited galvanostatically onto the stainless steel substrate from aqueous Ni(NO 3 ) 2 solution (0.01 M). Morphological, structural and chemical characteristics of the synthesized NiO were examined by means of scanning and transmission electron microscopy (SEM and TEM) as well as X-ray diffraction (XRD) and FT-IR spectroscopy. The XRD and TEM results revealed that the oxide products have well-crystallized cubic structure with capsule-like morphology of various length and diameters in the order of 20–70 nm and 10–30 nm, respectively. Capacitive performance of NiO nanocapsules were evaluated by cyclic voltammetry and galvanostatic charge/discharge measurements in a potential window between −0.2 and +0.5 V vs. Ag/AgCl. Electrochemical measurements revealed that the NiO nanocapsules have a specific faradaic pseudocapacitance as high as 307.2 F g −1 in 1 M KOH solution and good cycle life (approximately displayed 86.4% of its maximum capacitance after 3000 cycle discharging). These results showed that the prepared NiO nanostructure can be recognized as a promising candidate for the supercapacitor applications.