Ethanol-assisted hydrothermal synthesis and electrochemical properties of coral-like β-Co(OH)2 nanostructures

Highly uniform, porous beta-Co(OH)(2) nanostructures with an appearance reminding of certain spherical corals were synthesized via a facile, one-step hydrothermal route using ethanol-water mixtures as solvents. The rough surfaces of the nanostructures consist of numerous randomly distributed, interconnecting nanoflakes, resulting in a network-like structure with many cavities. The coral-like product has a high Brunauer-Emmet-Teller specific surface area of 163 m(2)/g. The diameter of the coral-like beta-Co(OH)(2) nanostructures is adjustable from 800 nm to 2 mu m. The effects of the ethanol/water ratio, the Co2+ concentration, the hydrothermal temperature, and the reaction time on the formation of the coral-like structures were investigated. Cyclic voltammetry and galvanostatic charge-discharge tests show that the beta-Co(OH)(2) possesses excellent capacitive properties. This is mainly attributed to the high porosity, which allows a deep penetration by electrolytes. (C) 2010 Elsevier Inc. All rights reserved.