Electron paramagnetic resonance and electron spin echo study of supported and unsupported vanadium oxides

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dc.contributor.authorLuca, Vittorio
dc.contributor.authorMacLachlan, Dugald
dc.contributor.authorBramley, Richard
dc.date.accessioned2015-12-13T23:35:12Z
dc.date.available2015-12-13T23:35:12Z
dc.date.issued1999
dc.date.updated2015-12-12T09:39:02Z
dc.description.abstractElectron paramagnetic resonance (EPR) and electron spin echo envelope modulation (ESEEM) spectroscopies have been used to characterize paramagnetic centers in crystalline and gel forms of vanadium pentoxide as well as vanadia supported on silica, titania, and magnesia. A number of different paramagnetic centers are observed in the bulk and supported vanadia phases that are characterized by their spin Hamiltonian parameters. ESEEM data for all the bulk vanadium oxide samples show intense modulation at the51V Larmor frequency. This modulation originates from interlayer VO2+ species in gel samples and from V4+ centers in crystalline oxides. The intensity of the51V modulation varies considerably from sample to sample depending on the specific nature of the paramagnetic center. For the supported vanadia samples, complex EPR spectra are obtained that show two classes of signals. Signals with narrow linewidths and resolved hyperfine structure are observed suggesting magnetically isolated V4+ in addition to dipolar exchange broadened signals. ESEEM spectroscopy reveals that the spectra observed for vanadia supported on silica are from surface bound vanadyl species that interact with predominantly diamagnetic surface vanadia clusters. In contrast, for vanadia supported on titania, the V4+ signals observed by pulsed EPR show no modulation. The absence of modulation is attributed to well dispersed surface vanadyl species and subsurface V4+(6c) centers. Vanadium supported on magnesia interacts to form new magnesium vanadate phases containing V4+(6c). It is shown that ESEEM is a valuable tool for characterizing vanadia supported on various oxides.
dc.identifier.issn1463-9076
dc.identifier.urihttp://hdl.handle.net/1885/93802
dc.publisherRoyal Society of Chemistry
dc.sourcePhysical Chemistry Chemical Physics
dc.subjectKeywords: magnesium oxide; silicon dioxide; titanium dioxide; vanadium; vanadium pentoxide; article; catalyst; chemical structure; crystal; electron spin resonance; gel; structure analysis; surface property
dc.titleElectron paramagnetic resonance and electron spin echo study of supported and unsupported vanadium oxides
dc.typeJournal article
local.bibliographicCitation.lastpage2606
local.bibliographicCitation.startpage2597
local.contributor.affiliationLuca, Vittorio, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationMacLachlan, Dugald, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationBramley, Richard, College of Physical and Mathematical Sciences, ANU
local.contributor.authoremailrepository.admin@anu.edu.au
local.contributor.authoruidLuca, Vittorio, u911358
local.contributor.authoruidMacLachlan, Dugald, u930596
local.contributor.authoruidBramley, Richard, u670043
local.description.notesImported from ARIES
local.description.refereedYes
local.identifier.absfor030207 - Transition Metal Chemistry
local.identifier.ariespublicationMigratedxPub25217
local.identifier.citationvolume1
local.identifier.doi10.1039/a900119k
local.identifier.scopusID2-s2.0-0033562153
local.identifier.uidSubmittedByMigrated
local.type.statusPublished Version

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