Electrocatalytic Deposition of Polypyrrole

In the presence of a small amount of bromide , the deposition of polypyrrole is possible at appreciably higher current densities than in the absence of a catalyst. The mechanism is assumed to involve the reaction of pyrrole with bromine in the form of Br 3 to give [Br 3 ] ⊖ and the pyrrole radical cation. The latter then undergoes addition at the 2 position with a second radical cation or with a neutral pyrrole molecule, a CC bond being formed. The dimers are readily oxidized further, resulting in the formation of polymers. The [Br 3 ] ⊖ ion is reoxidized at the electrode.