Nanostructured nickel hydroxides are galvanostatically deposited onto a stainless steel substrate by a plating bath of nickel sulfate, sodium acetate, and sodium sulfate at room temperature. The anodically deposited nickel hydroxide electrodes are highly porous and composed of interconnected nanoflakes about 12-16 nm in thickness. Pore size of the deposited electrode increases with decreasing the depositing current density. X-ray diffraction patterns show that the deposited nickel hydroxide converts into nickel oxide at annealing temperature above 300°C. Annealing temperature influences both the electrical resistance and the grain size of the electrode and, consequently, determines the capacitive behavior of the electrode investigated by cyclic voltammetry in 1 M KOH aqueous solution. An optimal annealing temperature of 300°C is obtained in terms of the electrode's specific capacitance. An electrode with larger pores deposited at lower current density has a higher specific capacitance because larger pores facilitate the ion diffusion rate. An electrode with smaller pore size deposited at higher current density exhibits more kinetically reversible behaviors, resulting in a better high-rate capability.
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