STUDY OF THE ANILINE OXIDATION PROCESS AND CHARACTERIZATION OF PANI FILMS BY ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY

The initial stages of the electropolymerization process of aniline on a Pt electrode in acid aqueous solutions (H2SO4 and HClO4), as well as the properties of the films formed at potentials corresponding to the first redox couple where the conducting reversible oxidized polymer s tate is generated, have been studied by electrochemical impedance spec troscopy (EIS). The kinetic parameters associated with the charge tran sfer reaction during the monomer oxidation and the concomitant diffusi on process to generate an oligomeric high-density region near the elec trode surface were calculated. The analysis of impedance data clearly shows that the frequency response of polyaniline (Pani) films is depen dent on the nature of the electrolyte in which the films were prepared . The electrochemical response of the Pani films formed in the presenc e of HClO4 gives rise to the conclusion that the rate of the redox pro cess become slower than that in H2SO4. (C) 1998 Elsevier Science S.A. All rights reserved.