ELECTROCATALYTIC SYNTHESIS OF POLYANILINE ON NONNOBLE METAL-ELECTRODES

Electrochemical synthesis (ES) of polyaniline (PAn) at the surface cov ered by an oxide film is realized at a significantly higher voltage th an is needed for the formation of a nonoveroxidized polymer. The invol vement of catalytic amounts of the salts of transition metals in ES of PAn essentially facilitates the process at Ti, Ta, Pb, Al and stainle ss steel electrodes. IrCI62- anion was found to be an effective cataly st. During ES, IrCI62- forms a complex with aniline, where Ir-IY oxidi zes aniline to a radical cation. The formation of radical cation is a limiting stage ES PAn. It is realized in a moment in the presence of I rCI62-, thus providing a significant decrease of the induction period at a potentiostatic synthesis and the lowering of a working potential at a galvanostatic synthesis. It is shown that the composition of the complex includes Ir-III and 2 aniline molecules, which form a paramagn etic dimer inside a coordination sphere. (C) 1997 by John Wiley & Sons , Ltd.