Characterization of supported Nb catalysts by ToF-SIMS

Saeed B. Bukallah, Marwan Houalla, David M. Hercules

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)


A series of Nb2O5/TiO2 catalysts were prepared by incipient wetness impregnation of TiO2 with aqueous solutions of niobium oxalate/oxalic acid. Eight different catalysts with Nb loadings of 0.48-8.5 wt.% Nb were prepared. Analysis of the time-of-flight secondary ion mass spectrometry (ToF-SIMS) spectra of Nb2O5/TiO2 catalysts shows the presence of monomeric, dimeric and trimeric NbxOy clusters at all loadings. This indicates that polymeric Nb oxide species are present even at loadings well below that corresponding to monolayer coverage (approximately 4.5 wt.% Nb). Moreover, it was found that the degree of aggregation of the niobia active phase increases with Nb loading. The tetrameric Nb oxide cluster was the largest fragment detected for amorphous Nb2O5. For Nb2O5/TiO2 catalysts the tetrameric Nb cluster was first detected in the 2.8 wt.% Nb catalyst. It is conclude that bulk-like Nb2O5 is present in catalysts containing ≥2.8 wt.% Nb (i.e. ≥60% theoretical coverage).

Original languageEnglish
Pages (from-to)818-822
Number of pages5
JournalSurface and Interface Analysis
Issue number12
Publication statusPublished - Dec 2000

ASJC Scopus subject areas

  • General Chemistry
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Materials Chemistry


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