AVS 47th International Symposium
    Surface Science Monday Sessions
       Session SS1-MoA

Paper SS1-MoA10
In Situ Soft X-ray Studies of CO Oxidation on Pt(411): Studies of Defect Reactivity

Monday, October 2, 2000, 5:00 pm, Room 208

Session: Model Catalysts at High Pressures
Presenter: H.D. Lewis, University of Michigan
Authors: H.D. Lewis, University of Michigan
D.J. Burnett, University of Michigan
A.M. Gabelnick, University of Michigan
J.L. Gland, University of Michigan
D.A. Fischer, National Institute of Standards and Technology
Correspondent: Click to Email
The oxidation of preadsorbed CO on a Pt(411) single crystal surface has been studied over a temperature range of 100 to 600 K and in oxygen pressures up to 0.002 Torr using temperature-programmed fluorescence yield near-edge spectroscopy (TP-FYNES) above the carbon K edge. CO desorption from the Pt(411) surface shows that two-site desorption from step and terrace sites occurs. CO desorbs from terrace sites at 365 K and at 460 K from step sites, showing that CO is more strongly bound at the step sites. At low oxygen pressures (10@super-7@ Torr) oxidation occurs in two steps, beginning at terrace sites and then proceeding to step sites. At higher oxygen pressures (10@super-4@ Torr), one step oxidation at both the terrace and step sites is observed. Measuring surface carbon concentration it was determined that 60% of the CO adsorbed on the Pt(411) surface was on step sites, while the remaining 40% occupied the terrace sites. Isothermal kinetic studies were performed to establish a more detailed understanding of the oxidation mechanism. Kinetic parameters obtained in high oxygen pressures compare favorably to those on the Pt(111) surface.