Electrochemical impedance studies on the electrochemical properties of poly(3-methylthiophene) in aqueous solutions

Abstract

Electrochemical impedance spectroscopy (EIS) measurements in a wide frequency range were used to study the electrochemical properties of poly(3-methylthiophene) (PMT) films. PMT was synthesized in acetonitril (AC) using BF 4 −, ClO 4 − and CF 3SO 3 − as doping anion and Li + as cation. The electrochemical characterization of these films was performed in aqueous solution using the same electrolyte for synthesis. Different parameters as electrolyte resistance, double layer capacitance, pore resistance, fractal dimensions, internal capacitance and charge resistance. SEM observation of PMT films provide strong evidence of the close relationship between type of electrolyte and their morphology, also is in good agreement with ac impedance results interpretation. The results are interpreted on the basis of models developed for intercalation electrodes in relation to the geometry and morphology of the polymer electrode. The results are discussed on the basis of the structural and chemical parameters of the anions and their interaction with the polymer. The discussion shows that the nature of the anion plays a major role on the electrochemical behavior of the polymer.