SUPERADDITIVE CATALYSIS OF HOMOGENEOUS REDOX REACTIONS WITH MIXED SILVER GOLD COLLOIDS

As silver can be more easily oxidized than gold, certain electrocatalytic reactions occur more rapidly with silver as catalyst than with gold. On the other hand, in the presence of halide and some other anions an autoinhibition of the silver-catalysed reaction takes place because of the formation of an insoluble silver salt at the surface of this metal. This inhibition can be avoided, however, if a small amount of gold was deposited on silver. With electrocatalytic oxidation of N,N-dimethyl-p-phenylenediamine as a model reaction, the advantage of a silver-gold colloid compared with pure silver or gold colloids can be demonstrated.