Synchrotron radiation photoemission studies of CO chemisorption on Pt/Ta(110) and Ni/Ta(110)
The effect of overlayer structure and electronic density near the Fermi level on CO chemisorption is studied for Pt or Ni deposited on Ta(110) using angle-resolved synchrotron radiation photoemission spectroscopy. Pt films form two-dimensional pseudomorphic islands at submonolayer coverage, but undergo a structural change to a close-packed Pt(111)-like structure at --0.7 monolayer coverage. Absence of CO induced photoemission features at monolayer coverage suggests that the CO--Pt bond has been weakened and this prevents the retention of CO on a close-packed Pt monolayer at room temperature. Close-packed Pt films three or more layers thick readily chemisorb CO. At liquid-nitrogen temperature, CO is retained on Pt/Ta(110), and photoemission features, such as the CO 4sigma shake-up satellite seen for weakly bonded CO on noble metals, appear for the CO phase chemisorbed on a Pt monolayer. This photoemission feature is absent for CO chemisorbed on thicker Pt films. Photoemission examination of the CO--metal bonding geometry suggests that the CO molecules lie close to the surface normal for both Pt monolayers and the thicker Pt films. From the photoemission data, we conclude that the CO--metal bond strength is reduced for CO--Pt/Ta(110). Comparable studies of CO on Ni/Ta(110) were not possible because the three-dimensional clustering of Ni produced a more complicated surface which had a number of inequivalent CO bonding sites.
- Research Organization:
- Brookhaven National Laboratory, Upton, New York 11973
- DOE Contract Number:
- AC02-76CH00016
- OSTI ID:
- 6371486
- Journal Information:
- J. Vac. Sci. Technol., A; (United States), Vol. 5:4
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CARBON MONOXIDE
CHEMISORPTION
NICKEL
PHOTOEMISSION
SORPTIVE PROPERTIES
PLATINUM
TANTALUM
ENERGY-LEVEL DENSITY
FERMI LEVEL
SYNCHROTRON RADIATION
THIN FILMS
BREMSSTRAHLUNG
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
ELECTROMAGNETIC RADIATION
ELEMENTS
EMISSION
ENERGY LEVELS
FILMS
METALS
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
RADIATIONS
SECONDARY EMISSION
SEPARATION PROCESSES
SORPTION
SURFACE PROPERTIES
TRANSITION ELEMENTS
360104* - Metals & Alloys- Physical Properties