Oxygen electrode reaction. Part 2.—Behaviour at ruthenium black electrodes

Charging curves and cyclic voltammetry were used to investigate the nature of the interaction of oxygen with an active ruthenium surface. Rather vigorous corrosion was observed under highly anodic conditions and the products, which must involve ruthenium ions in a variety of oxidation states, gave rise to a rather unusual catalytic process for oxygen evolution. Although ruthenium can adsorb large quantities of oxygen, its performance as a substrate for the oxygen reduction process is not very promising. Comparison with the reported behaviour on metals such as gold and platinum suggests that while d-band vacancies are essential for oxygen chemisorption, the concentration of such vacancies in ruthenium is too great. The overall result is that considerable overvoltage is required for oxygen reduction as the tightly bonded oxide film on the metal surface can either inhibit the reduction of molecular oxygen, or be itself reduced, even in the presence of dissolved oxygen, at potentials strongly cathodic to the reversible oxygen potential.