DIFFUSION OF CARBON-MONOXIDE AND OXYGEN ON PT(110) - EXPERIMENTS PERFORMED WITH THE PEEM

Citation
A. Vonoertzen et al., DIFFUSION OF CARBON-MONOXIDE AND OXYGEN ON PT(110) - EXPERIMENTS PERFORMED WITH THE PEEM, Surface science, 311(3), 1994, pp. 322-330
Citations number
33
Categorie Soggetti
Chemistry Physical
Journal title
ISSN journal
00396028
Volume
311
Issue
3
Year of publication
1994
Pages
322 - 330
Database
ISI
SICI code
0039-6028(1994)311:3<322:DOCAOO>2.0.ZU;2-Q
Abstract
Diffusion coefficients are determined by coverage profile analysis of photoemission electron microscope (PEEM) images. The diffusion coeffic ients for carbon monoxide and oxygen on a Pt(110) single crystal surfa ce were derived in the temperature range of 318 to 438 K for carbon mo noxide and 606 to 668 K for oxygen. Carbon monoxide does not show a pr onounced dependence of the diffusion coefficient on coverage but a sig nificant dependence on the surface reconstruction. Anisotropy of diffu sion is in the range of a factor of 2. In contrast, oxygen shows a ver y high anisotropy with diffusion occurring practically only parallel t o the crystallographic [110BAR] direction and a strong coverage depend ence. For an oxygen coverage less than 0.2 monolayer, the diffusion co efficient is higher by one order of magnitude than at high coverage. A ctivation energies for carbon monoxide diffusion are between 9 and 13 kcal/mol, while oxygen has an activation energy of 30 kcal/mol for low coverage and 40 kcal/mol for high coverage.