PH dependence of the voltammetric response of Polyaniline

Juliana Scotto,M Inés Florit,Dionisio Posadas

doi:10.1016/j.jelechem.2016.11.066

Abstract

Voltammetric studies of Polyaniline (Pani) films were carried out in solutions of 3.7M sulphate solutions of constant ionic strength and pH values comprised in the range between −0.6 and 3.0. The results show that if the voltammetric results are properly corrected by capacitive currents, according to Feldberg's model, it will be possible to obtain the potential dependence of the faradaic oxidation degree.The integrated anodic and cathodic charges are practically equal and independent of the electrolyte pH, in the range −0.6<pH<2.0. The pH dependence of the current peaks is qualitatively explained by the change in the interactions between the redox centres as a consequence of the changes in their protonation.

Highlights

Polyaniline (Pani) is an interesting electrochemically active macromolecule both, in the field of basic science as well as by its possible applications
At the pHs comprised in the range −0.6 b pH b 2.0, the peak current is linearly dependent on the sweep rate, v, the peak potential is independent of v and the charge scales with the film thickness
As the pH increases beyond about 2.0, and immediately after the positive switching potential, it is noted an increase of the cathodic current, suggesting the beginning of a different reduction process

Summary

Introduction

Polyaniline (Pani) is an interesting electrochemically active macromolecule both, in the field of basic science as well as by its possible applications. Many workers have studied the redox commutation of Pani modified electrodes and measured the dependence of the voltammetric parameters, potential and current peak values, on the electrolyte pH [2,3,4,5,6,7,8,9,10,11]. The first can be observed in the j vs E profile as a plateau after the charge transfer reaction has finished The presence of this capacitive contribution, added to the faradaic one, makes the experimental current/voltage response to differ from the pure faradaic one. The capacitive current cannot be separated from the faradaic one just from voltammetric measurements This model was applied to describe the voltammetric response of Pani in acid media [13]

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Conclusion