IMPEDANCE ANALYSIS OF POLYMER FILM ELECTRODES

A new model is elaborated which can explain some anomalies of the impedance spectra of polymer films on electrodes. The model assumes two capacitances associated with the double layers at the substrate/film and at the film/solution interfaces, respectively. The latter capacitance is considered as a constant phase element due to the inhomogeneity of the polymer network and to energetically non-equivalent bonding sites for counterions. The effect of a low dc current, ie a slow reaction of the redox sites in the film with solution species, is also investigated. The electrochemical impedances characteristic of the model have been derived. The simulated impedance spectra were compared with those obtained experimentally.