ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY OF TWIN WORKING ELECTRODES BRIDGED WITH CONDUCTING POLYMER LAYER

A new technique is described for electrochemical impedance spectroscop ic (EIS) investigations in the plane of a polymer layer coating an ele ctrode without crossing the interface polymer-electrolyte. For this pu rpose a twin-working electrode configuration was constructed, that con sists of two practically identical electrodes with a gap of a few micr ometers width between them. This gap was bridged by a polymer layer of polybithiophene. Its behaviour was studied during electrochemical dep osition on the twin electrode and during transition from insulating to conducting state upon oxidation. It is shown that for lower frequenci es the impedance spectra obtained depend predominantly on the polymer conductivity and are not determined by the macroscopic external polyme r/electrolyte interface. Contributions of capacitive ac currents that cross microscopic internal polymer-electrolyte interfaces in the deep pores of the polymer become considerable only in the higher frequency range.