ELECTROCHEMICAL PROPERTIES OF PANI FILMS FOR DIFFERENT COUNTERIONS INACIDIC PH ANALYZED BY IMPEDANCE TECHNIQUES

The bulk and interfacial transport properties of PANI free-standing me mbranes have been studied in acidic media with different counter-ions using the ac impedance technique with the four-electrode cell. The exp erimental data were compared to a theoretical expression recently prop osed, based on Nernst-Planck equation for mass transport and on slow d ischarge for ionic interfacial transfer. The ionic charge transfer res istance was found negligible for all counter-ions in acidic pH. For ea ch system, the polaronic diffusivity was in general between one and tw o orders of magnitude higher than the ionic one. A classification from the fastest to the slowest ionic species was established following th e order: chloride, sulphate, nitrate, phosphate and perchlorate. Copyr ight (C) 1996 Elsevier Science Ltd