On the interfacial impedance of the polymer electrodes. Models and experimental data

摘要

The interfacial impedance of the polyaniline and polypyrrole electrodes are analyzed. The electrical circuit models, including the CPE one, are compared and discussed. The analysis concerns experimental data on the polymer redox state, polymer thickness, bathing electrolyte concentration, and temperature dependencies of the electrode impedance. It is shown that the interfacial impedance of the thin film polyaniline electrode can be characterized by the two time constant capacitive model and/or the CPE model. The later suits better the reduced electrode. The interfacial resistance obtained from the two models is similar and it is considered to correspond to a sum of the ion transfer and adsorption resistances. It switches between the high and low values in a course of the reversible oxidation of polyaniline. The interfacial capacitances switch between the low and high values in a course of the reversible oxidation of polyaniline. On the other hand, the polypyrrole electrode is characterized better by the CPE model in the entire range of the reversible redox switching. It is argued that the CPE characteristics of the porous conducting polymer electrode originate from the complex mechanism of the interfacial process. The fractal nature of the geometrical origin seems to be demonstrated by the CPE characteristics of the undoped polyaniline.