The Behavior of Polypyrrole-Coated Electrodes in Propylene Carbonate Solutions

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Abstract
We report on the galvanostatic deposition of thin, highly reversible polypyrrole (PPy) films in dry 0.25 M TBAClO4/PC.TBAClO4/PC. Initially obtained films show narrow voltammetric peaks. After 100 potentiodynamic cycles up to 4.0 V, these films were almost completely converted to a structurally different, very stable form of PPy with the doping level twice as high as that of the freshly prepared PPy (reaching half an electron per pyrrole ring). The PPy films exhibited excellent cyclability in the potential range 2.0-4.0 V in the dry solution. Parallel X-ray photoelectron spectroscopy characterization of PPy films cycled up 4.0 V showed almost complete preservation of the π conjugation in the polymeric structure. We present evidence that the cycling of PPy films up to 4.6-4.8 V is reversible for the first few cycles. In such a potential window the maximum reversible charge obtained during the PPy film’s reduction corresponds to one electron per pyrrole ring. In parallel, irreversible oxidation takes place because the evolving dications located on the polymeric chains may be subjected to nucleophilic attacks from the residual molecules of H2OH2O or HCO3−HCO3− ions, which is in good agreement with the XPS data obtained. © 2002 The Electrochemical Society. All rights reserved.

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