Investigation of the electrochemical properties of poly(3,4-ethylenedioxypyrrole) films electrodeposited from aqueous solutions

Poly(3,4-ethylenedioxypyrrole) films on gold substrate were prepared by electropolymerization of ethylenedioxypyrrole monomer (EDOP) under potentiodynamic conditions in aqueous sodium sulfate solutions. The aim of the work was to characterize the gold | poly(3,4-ethylenedioxypyrrole) electrodes in aqueous sulfuric acid solutions and to compare the results with those of other studies that investigated similar systems. However, the experimental results obtained for the PEDOP modified electrodes significantly deviated from the expectations based on studies with similar systems. According to the results, two distinct types of polymer films were formed depending on the storage history of the monomer solutions. By using “fresh” monomer solutions polymer films with nearly ideal capacitive behavior were obtained and almost rectangular-shaped cyclic voltammograms could be observed in a rather broad potential range. Impedance spectra revealed that the charge transfer resistance between the substrate and the film was low. According to the SEM images the polymer layer on the gold substrate was relatively smooth with some small and short cracks. In contrast, working with “old” monomer solution that was not properly stored, the shapes of the cyclic voltammograms recorded at the Au | PEDOP | 0.1 M sulfuric acid (aq) electrode exhibited two peaks, a reduction peak at about −0.2 V vs. SSCE and an oxidation peak close to 0.2 V vs. SSCE, and the charge transfer resistances were considerably higher than those estimated for the electrode prepared using “fresh” monomer solutions. SEM images showed that the surface of the polymer film was extremely rough, with several wrinkles, creases and large cracks. This behavior was quite unexpected, because the two types of samples were prepared in the same way and only the storage histories of the two commercial monomer solutions were different.