Nanosized nickel oxide was synthesized by immersing the precursor NiHCNFe into 1 mol·L-1 KOH solution to obtain nickel hydroxide (Ni(OH)2) and then annealing in air at 300 ℃. X-ray diffraction (XRD) and transmission electron microscopy (TEM) tests showed the prepared samples were rhombohedral crystalline structure of NiO with uniform grain and with a diameter of about 8 nm. Electrochemical properties of NiO were examined by cyclic voltammetry, ac impedance and galvanostatic charge-discharge tests. The results demonstrated that nickel oxide had a good capacitive behavior and cyclability due to its nanostructure. The highest specific capacitance of nickel oxide was about 303 F·g-1 at a charge/discharge current density of 5 mA·cm-2 in 6 mol·L-1 KOH solution.
