Adsorption and reaction of gaseous H(D) atoms with D(H) adatoms on Pt(111) and Sn/Pt(111) surface alloys

Harald Busse, Michael R. Voss, Dmitri Jerdev, Bruce E. Koel, Mark T. Paffett

Research output: Contribution to journalArticle

7 Scopus citations

Abstract

The reaction of gas phase H(D) atoms with adsorbed D(H) atoms on Pt(111) and two different Sn/Pt(111) surface alloys was studied by temperature programmed desorption (TPD). The incident H(D) atoms were produced by thermal dissociation in a Pt tube source operated at 1300 K. The alloy surfaces were prepared in situ by vapor deposition of Sn onto a Pt(111) single crystal to form the (2 × 2) and (√3 × √3)R30°-Sn/Pt(111) surfaces, which have a well-defined structure and composition with relative Sn surface concentrations of 0.25 and 0.33, respectively. A kinetic barrier eliminates dissociative H2(D2) chemisorption on both of these surface alloys, but abstraction reactions of incident H(D) atoms with preadsorbed H or D adatoms occur at 110 K on Pt(111) and both Pt-Sn alloys. This is well below the temperatures for thermal recombination on these surfaces, indicating that the reactions proceed by a direct or pseudo-direct reaction mechanism. Values for the H→D abstraction cross-section, σR, on Pt(111) and the (2 × 2) and (√3 × √3)R30°-Sn/Pt(111) surface alloys were determined to be 0.21, 0.93, and 1.7 Å2, respectively. The corresponding D→H abstraction cross-sections for the two alloys were determined to be 0.8, and 1.5 Å2, respectively. The values of σR for both H→D and D→H reactions increase with ΘSn and indicate a significant structural sensitivity for H abstraction reactions. There is no significant kinetic isotope effect on either alloy surface, however there is evidence that incident H atoms are slightly more efficient in abstracting adsorbed D atoms than vice versa.

Original languageEnglish (US)
Pages (from-to)133-143
Number of pages11
JournalSurface Science
Volume490
Issue number1-2
DOIs
StatePublished - Sep 1 2001
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Materials Chemistry

Keywords

  • Alloys
  • Atom-solid interactions
  • Deuterium
  • Hydrogen atom
  • Low index single crystal surfaces
  • Platinum
  • Surface chemical reaction
  • Thermal desorption
  • Tin

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