Influence of potassium on the adsorption of hydrogen on Pt(111)

Journal Article · Thu Aug 20 04:00:00 EDT 1992 · Journal of Physical Chemistry

DOI:https://doi.org/10.1021/j100196a040· OSTI ID:281162

Gebhard, S C; Koel, B E ^[1]

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1. Univ. of Southern California, Los Angeles, CA (United States)

The influence of potassium adatoms on the adsorption and desorption kinetics of hydrogen on the Pt(111) single-crystal surface has been studied by temperature-programmed desorption (TPD). The authors report measurements of the dissociative sticking coefficient for H{sub 2} on Pt(111) over the entire range of coverages of H{sub (a)} and K{sub (a)} between zero and monolayer coverage. Small amounts of potassium strongly reduce the dissociative sticking coefficient for H{sub 2} on Pt(111) and eliminate the influence of a precursor in the adsorption kinetics. For example, when the K coverage, {circle_minus}{sub K}, is 0.043 (defined relative to the Pt(111) surface atom density) the initial sticking coefficient of H{sub 2} on Pt(111) at 150 K is reduced by a factor of 20. However, hydrogen adatoms on the K-modified surface are thermally stabilized compared to Pt(111). The peaks observed during H{sub 2} TPD occur at temperatures up to 150 K higher on the K-modified surface than for equivalent hydrogen coverages on K-free Pt(111). Comparisons with the Bi-modified surface demonstrate that the influence of K{sub a} exceeds local site blocking effects. The authors explain these observations in terms of a model in which K{sub a} modifies the electronic structure of the surface Pt atoms in nearby sites. 51 refs., 11 figs.

• Sponsoring Organization: USDOE
• OSTI ID: 281162
• Journal Information: Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 17 Vol. 96; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
ACTIVATION ENERGY
ADSORPTION
CHEMICAL REACTION KINETICS
HYDROGEN
PLATINUM
POTASSIUM
SORPTIVE PROPERTIES
TEMPERATURE DEPENDENCE