AVS 49th International Symposium
    Surface Science Monday Sessions
       Session SS1-MoM

Paper SS1-MoM11
Novel Low-Temperature Reactivity of Model Bimetallic Surfaces with Monolayer Coverages

Monday, November 4, 2002, 11:40 am, Room C-108

Session: Adsorption and Chirality
Presenter: N.A. Khan, University of Delaware
Authors: N.A. Khan, University of Delaware
J.G. Chen, University of Delaware
Correspondent: Click to Email
Bimetallic surfaces have gained considerable interest in fundamental surface science research because of their unique catalytic activity and electronic properties. By studying these surfaces at an atomic level, we can gain more insight into the origin of these novel properties. In this study, we have used various surface science techniques (TPD, HREELS, NEXAFS, and XPS) to investigate the properties of model bimetallic surfaces. We have shown that the one monolayer Ni/Pt(111) surface exhibits novel chemical reactivity, unlike the pure Ni(111) or Pt(111) surfaces. Temperature-programmed desorption (TPD) results indicate that hydrogen has a lower binding energy to the 1 ML Ni/Pt(111) surface than on the other two surfaces.@footnote 1,2@ In principle, a weak metal - hydrogen interaction should lead to an increase in the hydrogenation activity of other species on the surface. We have used other catalytically important probe molecules, such as cyclohexene and thiophene to further investigate this hydrogenation activity. XPS and NEXAFS also showed that the oxidation state and density of unoccupied states of one monolayer Ni/Pt(111) are similar to that of bulk Ni(111). In addition to studying the Ni/Pt(111) surface, we have also investigated the Ni/W(110) surface for comparison. On the Ni/W(110) surface, the probe molecules also undergo hydrogenation at a low temperature. However, the maximum activity occurs at about 0.4 ML Ni. At this coverage of Ni, Schmidthals, et. al. have found a large amount of surface strain.@footnote 3@ We will attempt to correlate this lattice mismatch to a novel chemical reactivity seen on the 0.4 ML Ni/W(110) surface. @FootnoteText@ @footnote 1@ H.H. Hwu, J. Eng Jr., J.G. Chen, J. Am. Chem. Soc. 124 (2002) 702. @footnote 2@ N.A. Khan, H.H. Hwu, J.G. Chen, J. Catal. 205 (2002) 259. @footnote 3@ C. Schmidthals, et. al. Surf. Sci. 402-404 (1998) 636.