Study on mass transport behaviors of polypyrrole and prussian blue films in aprotic solvents using the electrogravimetric techniques

Abstract

Ion and solvent transport behaviors of polypyrrole (PPy) and Prussian Blue films in aprotic solutions have been investigated with the cyclic electrochemical quartz crystal microbalance (EQCM) technique, the electrochemical impedance technique, and the electrogravimetric impedance technique. First, the mass transport mechanism of PPy and poly(N-methylpyrrole) (PMPy) films in an acetonitrile (AN) solution has been compared. Cations as well as anions take part in ion transport during the redox reaction of PPy films, and the break-in process occurs in the first cathodic scan. On the other hand, anion transport is dominant during the redox reaction of PMPy films, and no break-in process is observed. Solvent transport takes place in the same direction as cation transport in case of PPy films, whereas it occurs in opposite direction to anion transport in the case of PMPy films. Second, the dependence of mass transport behavior of poly(N-phenylpyrrole) (PPhPy) films on the electropolymerization condition has been revealed. It was found that the type of dopant anion and solvent used in the electropolymerization affects the amount and the direction of solvent transport during the redox reaction of a PPhPy film. It was also shown that the charge capacity and ionic resistance of a PPhPy film depends highly on the type of dopant anion and solvent used in the electropolymerization. The PPhPy film grown in a $PF_6^-$-containing solution shows larger charge capacity and lower ionic resistance than the film grown in a $ClO_4^-$-containing solution. Moreover, the PPhPy film grown in a propylene carbonate (PC) solution shows similar to or larger charge capacity and lower ionic resistance than the film grown in an AN solution. These dependences on the electropolymerization condition were discussed in connection with the morphology of a film. Finally, the mass transport behavior of Prussian blue (PB) films in AN and PC solutions has been investigated. It was found that cation trans...