Electropolymerization of Polyaniline in the Presence of Ferricyanide

Here, we demonstrate that electropolymerization of aniline in the presence of ferricyanide leads to incorporation of the ferricyanide anions into the resulting polyaniline (PANI) film and an increase of the apparent deposition rate. Simultaneous cyclic voltammetry (CV) and quartz crystal microbalance (QCM) measurements in background electrolyte show a change in counter ion ingress/egress during oxidation and reduction of the film: an “inverted” mass transport behavior is observed, suggesting a cation-exchange mechanism for maintaining charge neutrality during oxidation of the leucoemeraldine to emeraldine state of the polymer. The behavior of the PANI-ferricyanide film is compared with films polymerized in the presence of potassium hexacyanoruthenate(II), FeCl₃ and RuCl₃. The potassium hexacyanoruthenate(II) enhances the polymerization rate and alters the electrochemical behavior of the film, much like ferricyanide, while FeCl₃ and RuCl₃ do not induce such an effect. Spectroscopic measurements confirm the presence of ferricyanide and hexacyanoruthenate(II) in the polymer.