Electrochemical property of surface modified polypyrrole film with heteropoly anions

Summary form only given. Preparation of heteropoly anion modified polypyrrole on glassy carbon and their electrochemical properties were studied. Keggin-type heteropolymolybdate and heteropolytungstate were chosen in this study because of their distinct catalytic activity towards the reduction of oxygen and nitrite in the solution. Electrochemical polymerization and incorporation of poly-anions were performed in solution containing both chemicals. The first scan of cyclic voltammogram showed the polymer film grew via nucleation and growth mechanism. Electrochemical peaks from the film were from polymer itself and from the incorporated poly anions. They were similar to those obtained from the solution and were stable under pH value of 4.5. The peak potential due to polypyrrole shifted to cathodic direction by about 40 mV/pH, while those of poly anion´s peak exhibited cathodic shift of about 60 mV/pH. As the thickness of the film changed the charge transport mechanism also changed and the redox peaks shifted to cathodic direction. The amount of incorporated anions determined by electrochemical method linearly depended on the charge passed in the polymerization process. The apparent diffusion coefficient of incorporated poly-anions in the polymer film was determined to be in the order of 10/sup -9/ to 10/sup -10/ cm/sup 2//sec. Electrochemical quartz crystal microbalance technique provided some insight of the film formation and the incorporation of poly anion. Also the catalytic activity towards the reduction of oxygen and hydrogen peroxide will be discussed.