The mechanism of electrode passivation during the electrodeposition of polypyrrole from aqueous solutions containing fluoride anions

The electrodeposition of polypyrrole from an aqueous solution containing a fluoride salt as supporting electrolyte is associated with a self-passivation of the electrode, caused by an unusually low conductivity of the polymer. Conductivity values are deduced from impedance data and from a special analysis of the cyclovoltammograms recorded during the potentiodynamic synthesis. Ion exchange experiments, the deposition from mixed KF/KCl electrolytes as well as the completely different behaviour during poly(N-methylpyrrole) deposition lead to the conclusion that the positive charges in oxidized polypyrrole fluoride films are not located on the polymer backbone, but on the hydrogen atom of the pyrrole nitrogen. This system is stabilized by hydrogen bonds to the fluoride ion.