UNDERPOTENTIAL DEPOSITION AND ELECTROCATALYSIS

In the present review article an assessment of the catalytic role of foreign metal adatoms deposited at underpotentials is made with emphasis on the electrocatalysis of electrosynthetic and fuel cell reactions. In particular, heavy metal adatoms increase the catalytic activity of noble and transition metal electrodes for several different types of electrochemical reactions. The enhancement of the electrocatalytic activity of metal electrodes by underpotential deposited sub- and monolayers can: (i) permit electron-transfer processes to occur at much lower overpotentials (Examples of such systems include the reduction of oxygen and the oxidation of some organic fuels); (ii) improve the selectivity of the electrocatalyst surface. (Here examples would include the reduction of nitro and nitroso compounds and the catalytic hydrogenation of some unsaturated organic compounds; and (iii) in less extreme cases, lead to great improvement of the reversibility of redox electrodes.