The influence of surface defects on ethanol dehydrogenation versus dehydration on the UO2(111) surface

S V Chong, M A Barteau, Hicham Idriss

Research output: Contribution to journalArticle

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Abstract

The decomposition of ethanol has been investigated on Ar+-sputtered surfaces of a UO2(111) single crystal. X-ray photoelectron spectroscopy (XPS) of the U 4f peaks after sputtering for 1 h showed the presence of two distinct oxidation states: U4+ (U 4f(7/2) at 380.2 eV) and U-0 (U 4f(7/2) at 377.4 eV). Upon ethanol exposure at room temperature, the peak at 377.4 eV was attenuated, indicating that U-0 sites were oxidized to Ux+i(x less than or equal to 4). The presence of a mixture of oxidation states on the surface influenced the reaction products observed during temperature programmed desorption (TPD). While ethylene and acetaldehyde desorbed in one temperature domain (at 560 K) from stoichiometric UO2(111), an additional desorption domain (at 475 K) was observed over the substoichiometric surface. The ratio of acetaldehyde to ethylene produced was different in the two temperature domains. While this ratio was near unity for the 560 K domain, it decreased to ca. 0.5 for the 475 K peaks on the substoichiometric surface. The lower temperature reaction channel is likely associated with surface oxygen vacancies, as it leads to greater oxygen abstraction, forming ethylene from surface ethoxide species. (C) 2000 Elsevier Science B.V. All rights reserved.

Original languageEnglish
Pages (from-to)283-289
Number of pages7
JournalCatalysis Today
Volume63
Issue number2-4
DOIs
Publication statusPublished - 25 Dec 2000

Keywords

  • ethanol dehydrogenation
  • Ar+-sputtered surfaces
  • UO2(111)
  • ethanol dehydration
  • surface oxidation
  • SINGLE-CRYSTAL
  • REACTIVITY
  • 1-PROPANOL
  • URANIUM
  • surface oxidation
  • URANIUM

Cite this

The influence of surface defects on ethanol dehydrogenation versus dehydration on the UO2(111) surface. / Chong, S V ; Barteau, M A ; Idriss, Hicham.

In: Catalysis Today, Vol. 63, No. 2-4, 25.12.2000, p. 283-289.

Research output: Contribution to journalArticle

Chong, S V ; Barteau, M A ; Idriss, Hicham. / The influence of surface defects on ethanol dehydrogenation versus dehydration on the UO2(111) surface. In: Catalysis Today. 2000 ; Vol. 63, No. 2-4. pp. 283-289.
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AB - The decomposition of ethanol has been investigated on Ar+-sputtered surfaces of a UO2(111) single crystal. X-ray photoelectron spectroscopy (XPS) of the U 4f peaks after sputtering for 1 h showed the presence of two distinct oxidation states: U4+ (U 4f(7/2) at 380.2 eV) and U-0 (U 4f(7/2) at 377.4 eV). Upon ethanol exposure at room temperature, the peak at 377.4 eV was attenuated, indicating that U-0 sites were oxidized to Ux+i(x less than or equal to 4). The presence of a mixture of oxidation states on the surface influenced the reaction products observed during temperature programmed desorption (TPD). While ethylene and acetaldehyde desorbed in one temperature domain (at 560 K) from stoichiometric UO2(111), an additional desorption domain (at 475 K) was observed over the substoichiometric surface. The ratio of acetaldehyde to ethylene produced was different in the two temperature domains. While this ratio was near unity for the 560 K domain, it decreased to ca. 0.5 for the 475 K peaks on the substoichiometric surface. The lower temperature reaction channel is likely associated with surface oxygen vacancies, as it leads to greater oxygen abstraction, forming ethylene from surface ethoxide species. (C) 2000 Elsevier Science B.V. All rights reserved.

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