Abstract
The oxidation of the platinum (111) single crystal surface and the formation of platinumdioxide have been studied by in situ surface x-ray diffraction and x-ray reflectivity. At anoxygen partial pressure of 500 mbar and at temperatures from 520 to 910 K, theexperiments disclose the growth of two atomic layers of a bulk-like, strongly distortedα-PtO2.The epitaxial Pt oxide layer is oriented hexagon on hexagon with respect to the Pt(111) surface leadingto a (8 × 8) superstructure surface unit cell. In a second set of experiments, a 100 Å thick epitaxialPt(111) film on sapphire was exposed to oxygen. At 670 K and near atmospheric oxygenpressures we find the formation of a several angstrom thick oxide layer. After annealing thesample at 720 K in a vacuum the oxide layer desorbs, recovering the 100 Å thick Pt film.Subsequent oxidation at 720 K and reduction cycles lead to a slight increase in surfaceroughness and the formation of macroscopically visible holes in the Pt film. These resultspoint to a Pt re-dispersion which sets in during chemical reactions at atmosphericpressures.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call