AN INVESTIGATION OF SOME OF THE VARIABLES INVOLVED IN THE GENERATION OF AN UNUSUALLY REACTIVE STATE OF PLATINUM

As pointed out earlier, platinum subjected to severe pretreatment in 3.0 mol dm-3 H2SO4 at 60-degrees-C exhibits unusual redox activity. The effect, which in general form is highly reproducible, appears to be a manifestation of reversible premonolayer oxidation, the reduced form being an active state of platinum in which the metal atoms of are low lattice coordination number and the oxidized state is a hydrous oxide. The influence of a number of variables involved in the activation process was investigated. Anomalous oxidation of platinum clusters in the presence of dry oxygen gas, as reported recently from another laboratory, seems to be a further example of the same type of effect. The unusual redox response, which persisted despite subjecting the electrode surface to extensive further cycling, aqua regia and heating to redness in a gas flame, is unlikely to be due to an impurity. The absence of a response in base, despite the retention of the active layer in the latter, is also in agreement with predictions based on the hydrous oxide approach. A new scheme is presented in which both the monolayer oxide and hydrous oxide electrochemistries of the platinum metal/aqueous solution interface are combined,