Hybrid TiO2-SiO2 Organic/Inorganic Gels: Preparation, Characterization, and Temperature-Programmed Pyrolysis and Oxidation Studies

Edgar Lotero, David Vu, Chau Nguyen, Jennifer Wagner, Gustavo Larsen

Research output: Contribution to journalArticle

24 Scopus citations

Abstract

Permethylated cyclooligosiloxane rings, tetraethylortosilicate (TEOS), and Ti(iPr)2Cl2 were used to prepare hybrid TiO2-SiO2 xerogels. A number of solvents were ineffective for leaching the organic silicon from the samples at 336 K after several hours. The nitrogen desorption isotherms of these materials reveal that microporous structures with broad pore size distributions are generated upon gelation. Characterization of the samples by means of 29Si CP/MAS NMR shows incorporation of the "organic silicon" into the amorphous structure and also suggests a great extent of homogeneity in the proton distribution around all tetrahedral silicate centers. The thermal stability of these hybrid TiO2-SiO2 materials was studied under flowing nitrogen and air by means of temperature-programmed (TP) techniques, and in situ diffuse reflectance infrared spectroscopy (DRIFTS). The stability of the Si-C bond in the absence of oxygen is hardly influenced by the presence of Ti. All Ti-containing samples undergo high-temperature pyrolytic decomposition of the Si-C bond, even when oxygen was present. In the presence of oxygen, the Ti function catalyzes the complete oxidation of the remaining alkoxide groups, rather than Si-C bond oxidation. The thermal stability of the latter and the decomposition of alkoxide groups into olefins are confirmed by both TP methods and DRIFTS.

Original languageEnglish (US)
Pages (from-to)3756-3764
Number of pages9
JournalChemistry of Materials
Volume10
Issue number11
DOIs
StatePublished - Nov 1998

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

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