ISSN:
1572-879X
Keywords:
Hydrogen adsorption-on-platinum
;
hydrogen sticking probability
;
oxygen covered platinum
;
precursor state
;
energy dependent dissociation of D2
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract The dissociative adsorption of hydrogen on oxygen covered Pt(111) has been investigated using molecular beam techniques. The D2-sticking probability has been measured as a function of oxygen coverage (0 〈 ΘO 〈 0.25 ML) and angle of incidence for two incident energies, 14 and 63 meV. In addition, the order of the oxygen layer has been measured using thermal He-scattering. The measurements show clear evidence for the existence of two distinct adsorption processes both on the oxygen covered and on the clean Pt(111) surface, i.e. in the limit were ΘO approaches zero: an activated process which depends on the total oxygen coverage and a non activated process which is sensitive only to the amount of locally ordered oxygen. The non activated process can be explained in terms of a mechanism involving a short living precursor state. The picture for the activated process is less clear. The dependence of this process on the incident energy seems strong evidence for a mechanism involving a barrier to dissociation directly upon impact, whereas the dependence on the oxygen coverage supports previously reported experiments which seem to be only compatible with a precursor mechanism.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00773178
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