Influence of the Cation Nature of the Sulphate Salt on theElectrochemical Synthesis of Sulfate-Doped Polypyrrole

In this work, polypyrrole films were electrosynthesized from aqueous media onto a graphite-epoxyresin composite electrode (GCE) using sulphate ions as dopant. Potentiostatic electrosynthesis studieswere done using different salts as SO4-2source, namely: Na2SO4, Li2SO4, (NH4)2SO4 and K2SO4. Thepotentiometric response of the diverse Ppy-SO4-2films was evaluated by means of calibration plots;according to the slope sign the behavior of the different films can be classified in three responses:anionic, cationic and anionic-cationic. Such behaviors were observed for all synthesized films,independently of the sulphate salt used. When analyzing the current transients obtained for thedifferent salts, similarities were found for those with the same potentiometric behavior, but significantdifferences were observed when comparing transients of different potentiometric responses. From theanalysis of the experimental current transients it was determined that the nature of the cation of thesulphate salt influences the number density of active sites on the electrode surface where the Ppy-SO4-2is deposited. Moreover, the kind of Ppy-SO4-2potentiometric response also depends on the type ofcation used during the polymer electrochemical synthesis. According to the results obtained, someboundaries for the potentiostatic synthesis parameters are suggested to induce a specific potentiometricresponse.