The effect of the nature and the concentration of counter ions on the electrochemistry of poly(vinylferrocene) polymer film electrodes

Abstract

The effect of the nature and the concentration of counter ions on the cyclic voltammetric and chronoamperometric behavior of poly(vinylferrocene) (PVF) polymer film electrodes has been studied in different aqueous and acetonitrile electrolytes. The variation of the peak potentials and peak currents with the nature and concentration of counter ions is explained in terms of salt formation between the oxidized redox sites in the film and the counter ions as well as the polyelectrolyte behavior of the surface layer. The effect of the different counter ions of similar size on the cyclic voltammograms may be explained by assuming different structures and solubilities or complex formation constants of the ferrocenium salts formed in the course of electrochemical oxidation. The concentration of the supporting electrolyte affects the solubility and/or the complex formation of the oxidized product as well as the swelling of the film. With increasing electrolyte concentration the oxidized film adopts a more compact structures. It helps the electron exchange reaction between electroactive sites, but hinders the diffusion of counter ions. It is shown that this effect should be taken into consideration for the explanation of the behavior of polymer film electrodes.