Effect of anion concentration on the kinetics of electrochemical polymerization of pyrrole

The kinetics of the electrochemical polymerization of pyrrole were studied in 0.1 mol/l pyrrole, pH 2 aqueous solutions with a supporting electrolyte concentration of 0.2-4.0 mol/l by linear sweep voltammetry and chronoamperometry. The supporting electrolytes used include sodium tosylate, sodium nitrate, potassium chloride and sodium perchlorate. It was found that the anodic peak of pyrrole polymerization shifted to lower potential with the increase in the concentration of the solution anions in the linear sweep voltammograms. The chronoamperometric responses also depended on the concentration. In the solutions with the anion concentration lower than 0.5 mol/l, the polymerization reaction rate (current) is almost proportional to the anion concentration while it becomes almost independent of the anion concentration when the concentration is higher than I mol/l. Accordingly, a reaction mechanism involving the participation of solution anions in the cation-radical electropolymerization processes of pyrrole was proposed, from which a kinetic equation was deduced. (C) 1997 Elsevier Science S.A.