Activation of Au/γ-Al 2O 3 catalysts for CO oxidation: Characterization by X-ray absorption near edge structure and temperature programmed reduction

C. K. Costello, J. Guzman, J. H. Yang, Y. M. Wang, M. C. Kung, B. C. Gates, H. H. Kung

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Abstract

Gold catalysts supported on γ-Al 2O 3 (Au/γ-Al 2O 3) were prepared by deposition- precipitation of aqueous HAuCl 4 and, alternatively, by deposition of Au(CH 3)a(acac) from pentane solution. The samples were characterized by in situ XANES and temperature-programmed reduction and by their performance as CO oxidation catalysts at room temperature. The Au was found to be present as Au(III) in both as-prepared catalysts, and the Au(III) was stable upon exposure to reducing gases at room temperature. Reduction of Au(III) occurred at elevated temperatures, and the rate and extent of reduction were found to depend strongly on the reducing conditions. Water vapor facilitated reduction, but only after the sample had been reduced to some extent by CO or H 2. Exposure of an as-prepared catalyst to a catalytically reacting mixture of CO + O 2 at 100°C was effective in activating it, though to a lesser extent. The data indicate that zerovalent Au is necessary for catalytic activity, but there is no correlation between the activity and the extent of reduction, implying that cationic Au may play a role in the catalytic sites. Water or surface species derived from water also appears to play a significant role.

Original languageEnglish
Pages (from-to)12529-12536
Number of pages8
JournalJournal of Physical Chemistry B
Volume108
Issue number33
DOIs
Publication statusPublished - Aug 19 2004

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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