Abstract

The electro-oxidation of methanol was studied in both acid and alkaline media, on clean iridium and on iridium electrodes modified by underpotential deposition and/or submonolayer deposits of Cu, Ag, Bi, Cd, Hg, Tl, Re and Pb. The catalytic effects of these atoms for methanol oxidation in acid medium decrease in the sequence Pb almost-equal-to Bi > Tl > Cd > Cu > Hg. In alkali, with bare iridium the oxidation charges are 16 times larger than in acid, but the metal adatoms act as inhibitors. The results obtained in this work indicate that a favorable interaction among the adatom and the organic residue on the electrode surface probably exists. This interaction depends on the nature of the deposited metal.