EFFECT OF THE BATHING ELECTROLYTE CONCENTRATION ON THE CHARGE-TRANSPORT PROCESS AT POLY(O-AMINOPHENOL) MODIFIED ELECTRODES - AN AC-IMPEDANCE STUDY

The effects of ionic strength and film thickness on the transport prop erties of poly(o-aminophenol) (POAP) film electrodes were studied by i mpedance spectroscopy. The dependences of the characteristic impedance quantities (Warburg coefficient, resistance and redox capacitance at low frequency) on these external variables were interpreted on the bas is of two models: a transmission line and a modified electron hopping model. Analysis of experimental data by means of the transmission line model allowed us to separate the charge transport process within the film in terms of electronic and ionic contributions represented by the diffusion constants, D-e and D-x, respectively. Application of the el ectron hopping model only gave an effective diffusion coefficient, D-e ff. The diffusion coefficients D-e and D-x, in the first case, and D-e ff in the second case, depend upon the ionic strength and film thickne ss. Moreover, D-eff is very close to D-e. This proves that charge prop agation is dominated by electron transport in this polymer. (C) 1997 E lsevier Science S.A.