ELECTROCHEMICAL BEHAVIOUR OF POLYPYRROLE FILMS IN HIGHLY CONCENTRATED AQUEOUS ELECTROLYTES

Polypyrrole polymer films doped with large surfactant anions, dodecyl benzene sulfonate, (PPy/DBS) were deposited on quartz crystals using the galvanostatic electropolymerization technique. The electrochemical behavior of the PPy(DBS) films in highly concentrated aqueous electrolytes were investigated using simultaneous cyclic voltammetry and electrochemical quartz crystal microbalance (EQCM) techniques in order to study the effect of the concentration of the electrolytes on the cycling of the films. Aqueous electrolytes of 0.1 - 6 M LiCl as well as 0.1- 3 M CaCl2 were used for this investigation. During the first redox cycle, while large water movement is observed along with the counter ions in dilute electrolytes, such water transport in concentrated electrolytes is found to be very low. In highly concentrated LiCl aqueous electrolytes, the mass of the PPy/DBS film at the end of each redox cycle is found to drift. The change in mass depends on the concentration of the cycling electrolytes used and the number of cycles. The mass drift during cycling can be controlled by changing the concentration of the cycling electrolytes. Also, the redox behaviour of the PPy/DBS film in highly concentrated CaCl2 aqueous electrolytes implies the availability of a new cation CaCl+ in 3 M CaCl2 electrolytes.