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 within the conducting polymer in the high-frequency and low-frequency regions, respectively. The redox transitions between the different oxidation structures of PANI cause the polymer to behave as a pseudocapacitor, especially at potentials ≥200 mV. A combination of the respective equivalent circuits for the electrode completely coated with a PANI film and for a bare graphite substrate successfully represents the EIS spectra of the electrodes with partial coverage of the polymer. A comparison of the EIS and chronopotentiometric results reveals that the effects of the anions on the electrochemical behavior of PANI are more obviously illustrated by the EIS method.