Chemical and structural stability of porous thin film NiO nanowire based electrodes for supercapacitors

Nanowires of NiO were successfully synthesized using a simple hydrothermal route. The nanowires were characterized for phase composition and morphology by X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques, respectively. XRD analysis showed that the powders produced were of high purity cubic NiO phase. Selected area electron diffraction (SAED) analysis during TEM showed the growth direction of NiO nanowires in (1 0 0), while exhibiting an average diameter of ∼ 65 nm. BET analysis showed these nanowires exhibiting a surface area of 153.2 m2/g. These nanowires were electrophoretically deposited on titanium foils as thin layer (∼5 μm thickness) and were studied for their capacitive behavior as electrodes for supercapacitor applications. Image analysis and atomic force microscopy (AFM) studies revealed the thin film coating to be highly porous (>50%). Cyclic voltammetry (CV) studies on these electrodes exhibited a specific mass capacitance of 750 F/g with 12% capacitance fade at the end of 1000 cycles. The present study elucidates how NiO surface morphology and OH− adsorption/desorption behaviors underlying these electrodes impact the chemical and structural stability performance.

► NiO nanowires of average diameter ∼65 nm were synthesized by hydrothermal method.
► Porosity of NiO thin film was found to be greater than 50%.
► NiO nanowire electrodes showed specific mass capacitance of 750 F/g.