THE ELECTROCHEMICAL IMPEDANCE OF A FREESTANDING POLYPYRROLE MEMBRANE

Electrochemical impedance measurements of polypyrrole in 0.1 M KCl wer e carried out on film electrodes in asymmetrical configuration (metal- film-solution) and on free standing membranes in symmetrical configura tion (solution-film-solution) in a two-compartment electrochemical cel l with two Pt counter electrodes and two Ag/AgCl (sat. KCl) reference electrodes. Films of 7.5-20 mu m thickness were deposited on a micro-p orous gold sputtered polycarbonate foil as support by electropolymeris ation from aqueous solution of 0.07-0.1 M pyrrole monomer and 0.1 M KC I. The impedance of the membrane was measured as function of the film thickness and the redox potential. The data were analysed with a theor y of a macroscopically homogeneous porous membrane, previously develop ed for a porous layer coating on a metal electrode and here extended f or heterogeneous charge transfer between better conducting (stronger o xidised) regions and less conducting regions within the film. (C) 1998 Elsevier Science Ltd. All rights reserved.