KINETICS OF POLYPYRROLE ELECTROGENERATION ON PT THROUGH TAFEL SLOPES

A study of the Tafel slopes and the subsequent reaction orders, as a function of monomer and electrolyte concentrations, in different electrolytic medias, for polypyrrole electrogeneration, is presented. The evolution of the Tafel representations is similar in all the analyzed systems (acetonitrile, water and acetonitrile + 2% of water). Two straight lines with a net change of slope are always present. The change of the Tafel slope is associated to a change of the electrode mechanism, due to the evolution of the chemical nature of the electrode surface from a bare platinum electrode to a polypyrrole coated electrode. The empirical kinetics obtained from the region of lower slope values (coated electrode), are: Rp=[Pyrrole]x[ClO4-]y, with x = 0.5, for the three studied systems, and y = 0.5, 0.7, 0.5 for acetonitrile, water and acetonitrile/water solutions respectively, in agreement with reaction orders obtained from a gravimetric following of the electrogenerated polymer.