Quartz Crystal Microbalance-Based Evaluation of the Electrochemical Formation of an Aggregated Polypyrrole Particle-Based Layer

Electrochemical quartz crystal microbalance (EQCM) was used for the evaluation of conducting polymer polypyrrole (Ppy), which was formed by a sequence of potential pulses on a Au-plated EQCM disc. The Ppy layer was obtained from freshly prepared polymerization solution consisting of pyrrole that was dissolved in phosphate buffer. The main aim of the study was to determine some aspects of the Ppy layer formation process. The polymerization process was estimated by EQCM and chronoamperometry. The Cottrell equation was used for the integration of total charge that was passing through the electrochemical cell during the formation of the Ppy-based layer. It was found that the charge of the electrical double layer, which was estimated while applying an Anson plot, is negative. From this observation, it could be assumed that the pyrrole oxidation process could be well described by principles of heterogeneous kinetics. The negative value of the electrical double layer was the result of a charge-transfer restriction. This restriction of charge transfer could occur due to partial blocking of the electrode surface by an aggregated Ppy particle-based layer. Quartz crystal motional resistance (R) was taken into account during this research. Ppy layer formation is represented schematically on the basis of the obtained experimental results and analytical data.