MULTILAYER OXIDE-GROWTH ON PLATINUM UNDER POTENTIAL CYCLING CONDITIONS .1. SULFURIC-ACID-SOLUTION

Hydrous oxide growth on platinum under potential cycling conditions in 1.0 mol dm-3 H2SO4 yielded either a single or a two component product; the latter gave rise to two major reduction peaks in the region below 0.4 V (rhe). To obtain good reproducibility it was convenient to condition the electrode before use by a preliminary etch in aqua regia, followed by repeated (usually 5) hydrous oxide growth and reduction runs. With an upper cycling limit less than 2.1 V (rhe) there was a tendency for formation of only one hydrous oxide product which reduced just below 0.4 V (rhe). With a higher value for this upper limit an additional hydrous oxide component (which may contain incorporated sulphate species) was produced-the reduction of the latter yielded a second cathodic peak at ca. 0.2 V (rhe). A number of other variables in the system, eq oxide growth sweep-rate and cycling time, oxide reduction sweep-rate, and surface area changes were examined. A brief outline of the importance of hydrous oxides in some interfacial reactions is included. © 1990.