Modified Electrodes Type Doped Polypyrrole/Pure Titanium and their Electrochemical Characterization

Polypyrrole (PPY) films were electrodeposited at pure titanium from different aqueous solutions. The electropolymerization process was carried out by galvanostatic method. Cyclic voltammetry and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical properties of electrodes. The results indicate that the surfactant anion favors redox processes which are faster and more reversible than those associated to usual polypyrrole electrodes. In fact, while in PPY films doped by conventional, small anions (e.g., Cl−), the charge compensation is assured by uptake of the anions during oxidation and the release of the same anions during reduction, in the PPY films prepared in the presence of large-anions salts (e.g., sodium dodecylsulphate-SDS), the charge compensation appears to involve incorporation of cations since the large anions are not easily released from the polymer matrix. An equivalent circuit was proposed to successfully fit EIS data and the significant contribution of pseudocapacitance from polypyrrole was thus identified. EIS measurements on Ti/PPY film electrodes were carried out in the supporting electrolyte depending on the following parameters: PPY-film thickness, supporting electrolyte concentration c, temperature T, and polarisation potential E.