Electrochemical impedance characterization of polyaniline-coated graphite electrodes for electrochemical capacitors - effects of film coverage/thickness and anions

The electrochemical impedance spectroscopic (EIS) responses of polyaniline (PANI)-coated graphite electrodes are governed by the process occurring at the PANI \ electrolyte interface and the bulk faradaic redox transitions wi thin the conducting polymer in the high-frequency and low-frequency regions , respectively. The redox transitions between the different oxidation struc tures of PANI cause the polymer to behave as a pseudocapacitor, especially at potentials greater than or equal to 200 mV. A combination of the respect ive equivalent circuits for the electrode completely coated with a PANI fil m and for a bare graphite substrate successfully represents the EIS spectra of the electrodes with partial coverage of the polymer. A comparison of th e EIS and chronopotentiometric results reveals that the effects of the anio ns on the electrochemical behavior of PANI are more obviously illustrated b y the EIS method. (C) 2001 Elsevier Science B.V. All rights reserved.