Carbon monoxide reaction with UO2(111) single crystal surfaces: A theoretical and experimental study

S D Senanayake, A Soon, A Kohlmeyer, T Sohnel, Hicham Idriss

Research output: Contribution to journalArticle

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Abstract

The reaction of CO has been investigated on the surfaces of UO2 (111) single crystal. Over the stoichiometric surface CO does not adsorb at 300 K and no further reaction is noticed. Over UO2-x (prepared by Ar+ bombardment), CO molecules adsorb and in presence of traces of H-2 they couple to form acetylene molecules that desorb in two. temperature domains during temperature programmed desorption (TPD). In the presence of excess H2 the coupling product is found to be ethylene. X-ray photoelectron spectroscopy (XPS) of the core level shows the presence of an U 4f line at 377 eV on the UO2-x surface, attributed to U metal. This line disappears upon CO adsorption (5 L and above) at 300 K; indicating oxidation of U metal atoms by O from dissociatively adsorbed CO. XPS C Is shows that the only C containing species formed is carbide. Computation of a alpha-U metal 2d-periodic slab was also conducted using plane-wave pseudopotential in the density functional theoretical framework. Two modes of CO adsorption were considered: molecular and dissociative. The dissociative adsorption was found more energetically favoured by 0.46 eV. From TPD, XPS and computation results it is strongly suggested that CO is dissociatively adsorbed on UO2-x and that a stable U-C species is formed at 300 K. (c) 2005 American Vacuum Society.

Original languageEnglish
Pages (from-to)1078-1084
Number of pages7
JournalJournal of Vacuum Science & Technology. A, Vacuum, Surfaces, and Films
Volume23
Issue number4
DOIs
Publication statusPublished - Jul 2005
Event51st AVS International Symposium - Anaheim, CA, United States
Duration: 14 Nov 200419 Nov 2004

Keywords

  • uranium oxides
  • pseudopotentials
  • acetaldehyde
  • temperature
  • actinides
  • oxidation
  • catalysts
  • metals
  • furan
  • atoms

Cite this

Carbon monoxide reaction with UO2(111) single crystal surfaces : A theoretical and experimental study. / Senanayake, S D ; Soon, A ; Kohlmeyer, A ; Sohnel, T ; Idriss, Hicham.

In: Journal of Vacuum Science & Technology. A, Vacuum, Surfaces, and Films, Vol. 23, No. 4, 07.2005, p. 1078-1084.

Research output: Contribution to journalArticle

Senanayake, S D ; Soon, A ; Kohlmeyer, A ; Sohnel, T ; Idriss, Hicham. / Carbon monoxide reaction with UO2(111) single crystal surfaces : A theoretical and experimental study. In: Journal of Vacuum Science & Technology. A, Vacuum, Surfaces, and Films. 2005 ; Vol. 23, No. 4. pp. 1078-1084.
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abstract = "The reaction of CO has been investigated on the surfaces of UO2 (111) single crystal. Over the stoichiometric surface CO does not adsorb at 300 K and no further reaction is noticed. Over UO2-x (prepared by Ar+ bombardment), CO molecules adsorb and in presence of traces of H-2 they couple to form acetylene molecules that desorb in two. temperature domains during temperature programmed desorption (TPD). In the presence of excess H2 the coupling product is found to be ethylene. X-ray photoelectron spectroscopy (XPS) of the core level shows the presence of an U 4f line at 377 eV on the UO2-x surface, attributed to U metal. This line disappears upon CO adsorption (5 L and above) at 300 K; indicating oxidation of U metal atoms by O from dissociatively adsorbed CO. XPS C Is shows that the only C containing species formed is carbide. Computation of a alpha-U metal 2d-periodic slab was also conducted using plane-wave pseudopotential in the density functional theoretical framework. Two modes of CO adsorption were considered: molecular and dissociative. The dissociative adsorption was found more energetically favoured by 0.46 eV. From TPD, XPS and computation results it is strongly suggested that CO is dissociatively adsorbed on UO2-x and that a stable U-C species is formed at 300 K. (c) 2005 American Vacuum Society.",
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N2 - The reaction of CO has been investigated on the surfaces of UO2 (111) single crystal. Over the stoichiometric surface CO does not adsorb at 300 K and no further reaction is noticed. Over UO2-x (prepared by Ar+ bombardment), CO molecules adsorb and in presence of traces of H-2 they couple to form acetylene molecules that desorb in two. temperature domains during temperature programmed desorption (TPD). In the presence of excess H2 the coupling product is found to be ethylene. X-ray photoelectron spectroscopy (XPS) of the core level shows the presence of an U 4f line at 377 eV on the UO2-x surface, attributed to U metal. This line disappears upon CO adsorption (5 L and above) at 300 K; indicating oxidation of U metal atoms by O from dissociatively adsorbed CO. XPS C Is shows that the only C containing species formed is carbide. Computation of a alpha-U metal 2d-periodic slab was also conducted using plane-wave pseudopotential in the density functional theoretical framework. Two modes of CO adsorption were considered: molecular and dissociative. The dissociative adsorption was found more energetically favoured by 0.46 eV. From TPD, XPS and computation results it is strongly suggested that CO is dissociatively adsorbed on UO2-x and that a stable U-C species is formed at 300 K. (c) 2005 American Vacuum Society.

AB - The reaction of CO has been investigated on the surfaces of UO2 (111) single crystal. Over the stoichiometric surface CO does not adsorb at 300 K and no further reaction is noticed. Over UO2-x (prepared by Ar+ bombardment), CO molecules adsorb and in presence of traces of H-2 they couple to form acetylene molecules that desorb in two. temperature domains during temperature programmed desorption (TPD). In the presence of excess H2 the coupling product is found to be ethylene. X-ray photoelectron spectroscopy (XPS) of the core level shows the presence of an U 4f line at 377 eV on the UO2-x surface, attributed to U metal. This line disappears upon CO adsorption (5 L and above) at 300 K; indicating oxidation of U metal atoms by O from dissociatively adsorbed CO. XPS C Is shows that the only C containing species formed is carbide. Computation of a alpha-U metal 2d-periodic slab was also conducted using plane-wave pseudopotential in the density functional theoretical framework. Two modes of CO adsorption were considered: molecular and dissociative. The dissociative adsorption was found more energetically favoured by 0.46 eV. From TPD, XPS and computation results it is strongly suggested that CO is dissociatively adsorbed on UO2-x and that a stable U-C species is formed at 300 K. (c) 2005 American Vacuum Society.

KW - uranium oxides

KW - pseudopotentials

KW - acetaldehyde

KW - temperature

KW - actinides

KW - oxidation

KW - catalysts

KW - metals

KW - furan

KW - atoms

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M3 - Article

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