The Redox Switching Of Pani. Discussion Of Some Unsettled Problems

DIONISIO POSADAS; WALDEMAR A. MARMISOLLÉ; JULIANA SCOTTO; M. INÉS FLORIT

Szeged - Hódmezovásárhely

Workshop; 7th WEEM 2012. International Workshop on the Electrochemistry of Electractive Materials; 2012

The redox switching of Pani is a complex phenomena [1] in which several other phenomena accompain the charge transfer, some of them remaining unsettled. In this work it is present cyclic voltammetric (CV) and spectroelectrochemical results that contribute to understand some aspects of these processes. It is well known that during the voltammetric swept of Pani between the potential limits corresponding to the leucoemeraldine- emeraldine transformation, the peak potential of the anodic and cathodic traces do not coincide. Several explanations have been advanced to justify or to explain this phenomenon. In this work, it is shown experimental evidence that this is a truly hysteresis effect [2], independent of the speed with which the system is perturbed. Also, in the CV appears after the oxidation peak a so-called a "capacitive" current. It has been postulated that this current is proportional to the faradaic charge [3]. In this work, based on the spectroelectrochemical experiments, it is demonstrate that this is not so. Instead, it seems that this capacitive currrent is a consequence of a chemical conversion of the oxidized species onto others that, incidentally are the responsible of the polymer conductivity [4,5]. The spectroelectrochemical experiments also help understanding the nature of the process giving rise to the "capacitive" current. As the degree of doping increases, new species are formed, without charge transfer, at the expenses of the initially formed oxidized species.