THE ADATOM INCIPIENT HYDROUS OXIDE MEDIATOR MODEL FOR REACTIONS ON SILVER IN BASE

The adatom/incipient hydrous oxide mediator model for electrocatalysis at a metal/solution interface is outlined in a general manner and examined with particular reference to the behaviour of silver in base. A low level transition, involving less than 0.1% of the surface metal atoms, was observed at ∼0.4 V (RHE). Above this value (where Ag adatoms are assumed to oxidise to hydrous oxide) anodic reactions, e.g. HCHO oxidation or Ag dissolution in the presence of CN-, take place; below this value (where the adatom is unoxidized) cathodic processes, e.g. nitrobenzene or nitrate ion reduction, are catalysed at adatom sites. The role of subsurface oxygen, which may be an inhibiting factor in the case of nitrate reduction, is a feature requiring further investigation. © 1990 Chapman and Hall Ltd.