The Redox Switching Of Pani. Discussion Of Some Unsettled Problems

DIONISIO POSADAS; WALDEMAR MARMISOLLÉ; JULIANA SCOTTO; MARÍA INÉS FLORIT

Szeged

Workshop; 7th WEEM International Workshop on the Electrochemistry of Electroactive; 2012

International Society of Electrochemistry

The redox switching of Pani is a complex phenomena in which several other phenomena accompain the charge transfer, some of them remaining unsettled. In this work we present 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 scannings do not coincide. Several explanations have been advanced to justify or explain this phenomenon. In this work we show experimental evidence that this is a truly hysteresis effect 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. In this work, based on the spectroelectrochemical experiments, we 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. 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.