PLATINUM OXIDE FILM FORMATION REDUCTION - AN IN-SITU MASS MEASUREMENT STUDY

The growth and reduction of oxide films at Pt was studied using the quartz crystal microbalance technique. The compact alpha-oxide was shown to be anhydrous in nature (either PtO or PtO2). When the potential was extended into the hydrogen adsorption region, the electrode mass was seen to decrease, but then stabilized once the hydrogen evolution reaction commenced. These results, as well as the effect of the addition of chloride and ferrous ions on the mass measurements, have been interpreted in terms of ion adsorption-desorption processes. The mass change during the reduction of thin hydrous beta-oxide films was also monitored and yielded a mass-to-charge ratio consistent with a PtO(OH)2 film composition. Other mass data indicated that Pt dissolution can occur with repeated beta-oxide growth-reduction cycles and that some Pt may redeposit, given sufficient time at negative potentials.