Morphological and electrochemical studies of polypyrrole/Nafion(R)

Polypyrrole (PPy) was electrochemically synthesized from a NaBr solution onto a gold electrode coated with a thermally treated Nafion (R) film (Nf). In the reproducibly formed composite Nf/PPy, PPy was doped both by bromide and the sulfonate groups of Nf which can be seen in the cyclic voltammogram (CV) by a double peak in the first scans and by microprobe analysis. CVs and impedance spectroscopy indicate that, in NaBr solution, ion transport in the composite is maintained by sodium ions. The shape of the voltammograms is interpreted on a semiquantitative base. It was shown by lateral force microscopy for the first time that PPy grows from the electrode side into the ionic areas of Nf which, up to now, has only been an assumption. Composite films polarized to the redox potential (-583 +/- 10 mV) are mechanically freestanding membranes with both ionic and electronic conductivity.