Water reactions over stoichiometric and reduced UO2(111) single crystal surfaces

S D Senanayake, Hicham Idriss

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Abstract

The reaction of water has been investigated on the surfaces of stoichiometric and oxygen defected UO2(1 1 1) single crystal. On the stoichiometric surface most of the adsorption of H2O molecules at 300 K is reversible (>80%). The remaining water on the surface desorbs in two TPD peaks at 400 and 530 K with no evidence for H-2 formation. On the contrary on Ar+-sputtered surfaces, water is strongly adsorbed. The Ar+-sputtered surfaces contained large amounts of U metal or U cations in lower oxidation state than +4 (a shoulder at BE approximate to 377 eV). Upon H2O adsorption at room temperature most of the shoulder at 377 eV has disappeared suggesting a dissociative adsorption of water molecules. Further evidence of water dissociation was given by H-2 desorption during TPD. The amount of desorbed H-2 tracked the extent of surface reduction. A complex set of H-2 desorption (three peaks) was seen during TPD. These peaks were both sensitive to prior surface reduction and surface coverage. (C) 2004 Elsevier B.V. All rights reserved.

Original languageEnglish
Pages (from-to)135-144
Number of pages10
JournalSurface Science
Volume563
Issue number1-3
Early online date26 Jun 2004
DOIs
Publication statusPublished - 10 Aug 2004

Keywords

  • atom-solid interactions
  • electron-solid interactions
  • Auger electron spectroscopy
  • low energy electron diffraction (LEED)
  • X-ray photoelectron spectroscopy
  • thermal desorption
  • water
  • uranium oxide
  • ray photoelectron-spectroscopy
  • uranium oxides
  • vapor
  • polycrystalline
  • adsorption
  • acid

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