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
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.