Monomeric vanadium oxide on a θ-Al 2O 3 support

A combined experimental/theoretical study

Hack Sung Kim, Stan A. Zygmunt, Peter C Stair, Peter Zapol, Larry A. Curtiss

Research output: Contribution to journalArticle

43 Citations (Scopus)

Abstract

A combined experimental and theoretical study of vanadium oxide monomers on a θ-alumina surface under different environments has identified four different structures. Deep UV Raman results suggest that vanadia is attached predominantly to an aluminum site that was an isolated terminal Al - OH group on the θ-alumina surface. The preresonance Raman spectra for vanadium oxide supported on θ-alumina with a very low VO x surface density show three distinct V=O bands under dehydrated conditions. The observed frequencies match well with the calculated stretching frequencies from B3LYP density functional theory for tridendate, bidendate, and molecular structures of vanadium oxide monomers on a dehydrated surface. The free energies calculated for these three structures from density functional theory as a function of temperature suggest that all three could exist on the surface with the tridentate structure being the most stable of the three on the dehydrated surface. Different structures and different degrees of vibrational coupling of V - O to V=O modes may cause the appearance of three V=O bands in the preresonance Raman spectra. On the hydrated surface, the Raman spectra show a V - O band, in agreement with the calculated frequency for a monodentate structure on this surface. Finally, the calculated free energies of hydrated and dehydrated surfaces indicate a transition from a hydrated to a dehydrated θ-alumina surface occurs at around 600 K at 10 -6 atm pressure of H 2O.

Original languageEnglish
Pages (from-to)8836-8843
Number of pages8
JournalJournal of Physical Chemistry C
Volume113
Issue number20
DOIs
Publication statusPublished - May 21 2009

Fingerprint

Vanadium
vanadium oxides
Oxides
Aluminum Oxide
Alumina
aluminum oxides
Raman scattering
Raman spectra
Free energy
Density functional theory
monomers
Monomers
free energy
density functional theory
Aluminum
Molecular structure
Stretching
molecular structure
aluminum

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Electronic, Optical and Magnetic Materials
  • Surfaces, Coatings and Films
  • Energy(all)

Cite this

Monomeric vanadium oxide on a θ-Al 2O 3 support : A combined experimental/theoretical study. / Kim, Hack Sung; Zygmunt, Stan A.; Stair, Peter C; Zapol, Peter; Curtiss, Larry A.

In: Journal of Physical Chemistry C, Vol. 113, No. 20, 21.05.2009, p. 8836-8843.

Research output: Contribution to journalArticle

Kim, Hack Sung ; Zygmunt, Stan A. ; Stair, Peter C ; Zapol, Peter ; Curtiss, Larry A. / Monomeric vanadium oxide on a θ-Al 2O 3 support : A combined experimental/theoretical study. In: Journal of Physical Chemistry C. 2009 ; Vol. 113, No. 20. pp. 8836-8843.
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