Two-dimensional phase transition in the electroreduction of heptyl viologen on polycrystalline silver in aqueous media

In aqueous media, the cation radical of heptyl viologen, HV.+, forms a two- dimensional (2D) phase on a polycrystalline silver electrode. The phase res ults from the reduction of HV2+ molecules adsorbed on the electrode and con sists of the cation radical salt and bromide as counterion; it is dissolved through gradual nucleation and growth of vacancies, which take place simul taneously with a Langmuir-type desorption process. (C) 2001 Elsevier Scienc e B.V. All rights reserved.