Collect. Czech. Chem. Commun. 1987, 52, 1097-1114

Interfacial interactions and the heterogeneous one-electron reduction of methyl viologen

Michael Heyrovský and Ladislav Novotný

The J. Heyrovský Institute of Physical Chemistry and Electrochemistry, Czechoslovak Academy of Sciences, 118 40 Prague 1


The one-electron reversible electroreduction of methyl viologen to its radical cation in aqueous solutions on mercury electrodes proceeds, according to potential, concentration and time of electrolysis, in various ways. Methyl viologen is adsorbed in flat orientation at the electrode surface; it undergoes a surface redox process in π-interaction with the metal in a potential range positive by about 0.2 V of the beginning of the electroreduction. The actual reduction starts by electron transfer followed by adsorption of the radical cation and, at higher concentrations and in a narrow potential range, by crystallization at the electrode surface of a salt of the radical cation. In solution near the electrode the radical cation dimerizes and the dimer also adsorbs at the electrode. In the region of the standard redox potential and more negative the reduction proceeds by electron transfer from the electrode covered by a layer of the radical cation or of its dimer.