Direct low-temperature deposition of crystallized CoOOH films by potentiostatic electrolysis

Cobalt oxide films were deposited onto nickel electrodes from 25 up to 90degreesC at a constant potential of 0.5 V vs. SCE from a pH 7.4 nitrate solution containing 0.09 mol L-1 Co(II). Above 60degreesC, scanning electron microscopy and X-ray diffraction (XRD) experiments reveal that the films are constituted of crystallized grains. At 90degreesC the crystallite size is measured at ca. 34 nm. XRD experiments show that the crystallized product is composed of CoOOH, and Raman spectroscopy shows the formation of this compound between 40 and 90degreesC. Between room temperature and 90degreesC, the deposition rate is increased by an order of magnitude and the deposit crystallization has a favorable effect on the faradaic deposition efficiency. It may also favor the mechanical stability in temperature of this deposit when used as cobalt oxide-based protective coating of the molten carbonate fuel cell nickel cathode. (C) 2004 The Electrochemical Society. All rights reserved.