Quantifying accessible sites and reactivity on titania-silica (photo)catalysts: Refining TOF calculations

Todd R. Eaton, Michael P. Campos, Kimberly A. Gray, Justin M Notestein

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

It can be difficult to determine the number of active atoms accessible to the fluid phase in mixed oxide catalysts, as required for obtaining true turnover frequencies (TOF). Here, we utilize the selective titration of surface Ti atoms with phenylphosphonic acid (PPA) on TiO2-SiO2 materials to estimate the number of reactant-accessible sites. TiO 2-SiO2 composites were synthesized over a range of Ti loadings from grafting of titanocene dichloride (Cp2TiCl2) or tetraethoxy orthotitanate (TEOT) on SiO2 and sol-gel co-hydrolysis of Si and Ti alkoxides. The materials were characterized by DRUV-vis, XRD, BET, and XANES. Despite the significant morphological and electronic differences, materials prepared by Cp2TiCl2 and TEOT yielded a near-constant TOF of 0.14 h-1 (±0.04) across Ti loadings, for benzyl alcohol photooxidation, when normalizing rates by sites titrated by PPA. The fraction of Ti atoms titrated by PPA was strongly dependent on synthesis method and surface density. PPA titration and benzyl alcohol photooxidation may be useful measures of surface accessibility in other supported oxides.

Original languageEnglish
Pages (from-to)156-165
Number of pages10
JournalJournal of Catalysis
Volume309
DOIs
Publication statusPublished - 2014

Fingerprint

refining
Silicon Dioxide
Refining
reactivity
titanium
Titanium
Silica
silicon dioxide
Benzyl Alcohol
catalysts
acids
Catalysts
Photooxidation
Acids
photooxidation
Titration
titration
Atoms
Oxides
alcohols

Keywords

  • Active site
  • Photocatalysis
  • Supported oxide
  • Titania

ASJC Scopus subject areas

  • Catalysis
  • Physical and Theoretical Chemistry

Cite this

Quantifying accessible sites and reactivity on titania-silica (photo)catalysts : Refining TOF calculations. / Eaton, Todd R.; Campos, Michael P.; Gray, Kimberly A.; Notestein, Justin M.

In: Journal of Catalysis, Vol. 309, 2014, p. 156-165.

Research output: Contribution to journalArticle

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