STABILITY OF PRUSSIAN BLUE FILMS ON ITO ELECTRODES - EFFECT OF DIFFERENT ANIONS

Transformation of insoluble newly deposited Prussian Blue (PB) into the soluble structure stabilizes the film and allows its total oxidation to Prussian Yellow. The stability of PB films in electrochemical processes in successive potential cycling experiments and under long-term chemical attack by an electrolyte depends not only on the cation that takes part but also on the nature of the anion present. In aqueous media, the sulphate ion clearly destabilizes the crystalline structure whereas the nitrate ion favours stabilization. Initial changes in the voltammograms recorded immediately after the spectroscopic tests have been detected in all media. During the immersion period water molecules and ions enter the film and affect the redox processes. With time the ions arrange themselves in the heart of the lattice and the water molecules are lost, and the blocking of the redox processes disappears.