Electrochemical impedance studies on oxidative degradation,overoxidative degradation,deactivation and reactivation of conducting polymers

摘要

Electrochemical impedance spectroscopy (EIS) measurements in awide frequency range were used to study the oxidative degradation,overoxidative degradation, deactivation and reactivationphenomena in polythiophene (PT) films on Pt electrode doped fromaqueous solution of lithium trifluoromethanesulphonate (LiTFMS).The different parameters as electrolyte resistance, double layercapacitance, pore resistance, fractal dimensions, internalcapacitance and charge resistance were derived. In addition, theyfurnish information about the different phenomena that can occurin the polymer film during the doping process. SEM observation ofPT films provided strong evidence of the close relationship betweenthe polarization potential, deactivation, reactivation and theirmorphology, also in good agreement with ac impedance resultsinterpretation. The results are interpreted on the basis of modelsdeveloped for intercalation electrodes in relation to the geometryand morphology of the polymer electrode. The deactivated PT filmscould reactivate by polarizing at a highly positive potential. Themechanisms of degradation, deactivation and reactivation are also discussed.