Cobalt hydroxide ultra-fine nanoparticles with excellent energy storage ability

Pulse current deposition was applied for the first time in the cathodic electrodeposition of cobalt hydroxide from nitrate bath and ultrafine nanoparticles of β-Co(OH)2 were prepared via this route. The crystal structure and morphology of the prepared Co(OH)2 were analyzed by X-ray diffraction spectroscopy, scanning and transmission electron microscopes. The XRD analysis revealed that the deposited hydroxide has a pure brucite-like phase of Co(OH)2. Morphological characterization by SEM and TEM revealed that the prepared β-Co(OH)2 is composed of well-dispersed ultrafine particles with size of about 5 nm. The energy storage ability of the prepared nanoparticles was studied by means of cyclic voltammetry (CV) and galvanostatic charge–discharge tests in 1 M KOH. The nanoparticles showed an excellent energy storage ability, where they delivered an energy density of 0.105 Wh/g with coulombic efficiency of 91.8%. Result of this work showed that pulse current cathodic electrodeposition can be recognized as a facile route for the preparation of very fine nanoparticles of cobalt hydroxide.