Ion Movements during Redox Switching of Polypyrrole — Experiment and Simulation

Abstract

Diffusion I Electrochemistry I Quartz Microbalance I Transport PropertiesOxidation of pyrrole yields a charged polymer film with incorporated anions. During the following reduction electroneutrality can be maintained by expulsion of these anions or by incorporation of cations. The contribution of both processes to the overall charge transport is found to depend strongly on the formation potential during polymerization. The redox process of polypyrrole formed at + 1 .O V vs. Agl AgCl is accompanied by a change in mass, which can be interpreted by a simultaneous transport of anions and cations. A lower formation potential leads to a separation of the charge transport in an either anion or cation dominated region. These differences are related to a cathodically shifted first reduction which occurs if a low formation potential was used. The charge transfer at the electrode and at the polymersolution interface is illustrated by a physical model. It consists of an (E)"-C-(E),,, mechanism for the redox behavior of the polymer and a first-order reaction for incorporation and expulsion of ions. Computed voltammograms and mass curves are presented for different situations and compared to experimental conditions.

Effect of electrical conditions on an impedimetric immunosensor based on a modified conducting polypyrrole

“…the increasing of C f with the potential is related to the doping level of the film, as already observed in [29,42]. The doping process of the polypyrrole layer also leads to a slight increase of the thickness of the film by the swelling of the polymer layer due to incorporation of the counter ions, however, this will have a negligible effect on the change in the polymer capacitance.…”

Electrochemical properties of porphyrin-doped polypyrrole films

“…One possibility to show this phenomenon is to decrease the redox-activity of the PPy film through the depression of the mobility of the anions in this film. This result can be achieved by increasing the compactness of the PPy film by decreasing the rate of electrodeposition of the polymer [29][30][31][32]. In this part of the work PPy films were electrodeposited at low current density with a total charge Q s = 0.08 C cm À2 .…”

Polypyrrole Conducting Electroactive Polymers: Synthesis and Stability Studies

“…During the following reduction, electroneutrality can be maintained either by expulsion of these anions or be incorporation of cations 70 . The pyrrole units have positive charges, which are balanced by anions.…”