Cathodic electrodeposition of cobalt oxide films using polyelectrolytes

Composite films consisting of cobalt hydroxide and polyelectrolytes, such as poly(diallyldimethylammonium chloride) (PDDA) and polyethylenimine (PEI), were obtained by electrodeposition. In the proposed method, electrophoretic deposition of PDDA macromolecules or PEI–Co2+ complexes has been combined with cathodic electrosynthesis of cobalt hydroxide. By varying the concentration of the polyelectrolytes in solutions, the deposition time and the current density, the amount of deposited material and its composition can be varied. The composite deposits have been studied by scanning, transmission and atomic force microscopy, X-ray diffraction and thermogravimetric analysis. The obtained results have been compared with the results of investigation of pure cobalt hydroxide films. Heat treatment of the deposits resulted in decomposition of the hydroxide precursor and burning out of polymer to form cobalt oxide films. This method enables the formation of thick nanostructured oxide films.