The Electrocatalytic Behavior of Cobalt (and Iron) Electrodes at Low Potential in Base

The electrocatalytic behavior of cobalt is of particular interest in electroless metal deposition. The oxidation of several reducing agents used in this area, e.g. , hydrazine, formaldehyde, dimethylamine borane, and hypophosphite, at cobalt electrodes in base was investigated using cyclic voltammetry. Some of these species reacted at quite low potentials and the results were explained in terms of the incipient hydrous oxide mediation model of electrocatalysis. Analogies with recent results obtained for similar reactions on gold and copper were pointed out; little reaction was observed in the case of formaldehyde. This may be due to strong surface deactivation or inability of the metal to catalyze some intermediate step in the reaction. The behavior of cobalt is complicated by the fact that four oxidation states (0, I , II , and III) are involved at potentials below 1.30V (RHE), along with dissolution and passivation phenomena. While the activity of cobalt for any of these reactions was not dramatic, that of iron was virtually negligible. The latter may be due to ( i ) absence of an Fe(I) species, and ( ii ) oxidation of this metal commenced at a potential where the coverage of the surface is quite high. The presence of this hydrogen was assumed to inhibit interaction with other substances.