K.P. Vidanapathirana

Ion movement in polypyrrole/dodecylbenzenesulphonate films in aqueous and non-aqueous electrolytes

Abstract The electrochemical characteristics during the redox process of polypyrrole (PPy) films, prepared using dodecylbenzenesulphonate (DBS−) dopant species, have been investigated using a combination of cyclic voltammetry and Electrochemical Quartz Crystal Microbalance (EQCM) measurements. Investigations were carried out using aqueous and non-aqueous electrolytes to study the effect of solvent on the ion movement during redox processes. When PPy films are cycled in aqueous electrolytes transport of both anion and cation occurs during oxidation and reduction. However, when cycled in the non-aqueous electrolyte propylene carbonate (PC) only anion movement takes place.

Determination of ionic carriers in polypyrrole

Abstract The successful use of conducting polymers for actuators depends on the ability to control force and position precisely by the application of a potential. The reversible oxidation and reduction of the polymer backbone is accompanied either by the insertion/expulsion of anions, by the expulsion/insertion of cations, or by a more complicated mixture of the two cases. The identity of the mobile ion has been elucidated for three polypyrrole (PPy) based systems by using the Nernst equation to interpret the dependence of the peak potentials in voltammograms on electrolyte concentration. Using the LiClO 4 /propylene carbonate electrolyte, the ClO 4 − ion is the main mobile species, whereas when using LiClO 4 /acetonitrile it is the Li + ion. The switch in mechanism caused by the change of solvent, which does not formally enter into the oxidation/reduction equation, shows that the effect depends on finely balanced interactions between the ions, the polymer and the electrolyte solvent. When using a large, immobile anion (dodecyl benzene sulphonate) incorporated in PPy, the results in the NaCl/H 2 O electrolyte indicate mainly Na + ion motion, as expected. Simultaneous cyclic voltammetry and quartz crystal microbalance measurements indicate that the Na + ions are accompanied by a large number (10–20) of H 2 O molecules. Force measurements show that the full variation in force occurs over a relatively small potential range.

The influence of preparation conditions on the electrical conductivity of poly-N-methylpyrrole films

Electro-active poly-N-methylpyrrole (PNMP) films have been galvanostatically polymerized under a range of conditions. The influence of the conditions used in electropolymerization, such as electrolyte concentration, current density, type of doping anion, and temperature during polymerization on the electrical conductivity has been investigated. The conductivity was measured by the in situ method using a specially prepared two-band microelectrode. The current density used during the polymerization has a considerable influence on the conductivity, as earlier observed for polypyrrole in non-aqueous electrolytes. The conductivity changes with the size of the anion and the concentration of the electrolyte as well as on the temperature at which the polymerization was carried out. Polymer films formed at relatively higher temperatures had lower conductivities and were not able to insert as many counterions, indicating that the films formed were less perfect. At higher temperatures the increased rates and numbers of side reactions may be competing with the ideal one-dimensional polymerization process.

Investigation of a Pseudo Capacitor with Polyacrylonitrile based Gel Polymer Electrolyte

Pseudo capacitors belong to one group of super capacitors which are consisted with non carbon based electrodes. As such, conducting polymers and metal oxide materials have been employed for pseudo capacitors. Conducting polymer based pseudo capacitors have received a great attention due to their interesting features such as flexibility, low cost and ease of synthesis. Much work has been done using liquid electrolytes for those pseudo capacitors but has undergone various drawbacks. It has now been realized the use of solid polymer electrolytes as an alternative. Among them gel polymer electrolytes (GPEs) are in a key place due to their high ambient temperature conductivities as well as suitable mechanical properties. In this study, composition of a polyacrylonitrile (PAN) based GPE was optimized and it was employed as the electrolyte in a pseudo capacitor having polypyrrole (PPy) electrodes. GPE was prepared using ethylene carbonate (EC), propylene carbonate (PC), sodium thiocyanate (NaSCN) and PAN as starting materials. The maximum room temperature conductivity of the GPE was 1.92 × 10 Scm for the composition 202.5 PAN : 500 EC : 500 PC : 35 NaSCN (by weight). Performance of the pseudo capacitor was investigated using Cyclic Voltammetry technique, Electrochemical Impedance Spectroscopy (EIS) technique and Continuous Charge Discharge (GCD) test. The single electrode specific capacity (Cs) was found out to be 174.31 F/g using Cyclic Voltammetry technique at the scan rate of 10 mV/s and within the potential window -1.2 V to 1.2 V. The same value obtained using EIS was about 84 F/g. The discharge capacity (Cd) was 69.8 F/g. The capacity fade over 1000 cycles was rather a low value of 4%. The results proved the suitability of the pseudo capacitor for improving the performance further.