title: Low-temperature oxidation of carbon monoxide with gold(III) ions supported on titanium oxide.
abstract: Au/TiO2 catalysts prepared by a deposition-precipitation process and used for CO oxidation without previous calcination exhibited high, largely temperature-independent conversions at low temperatures, with apparent activation energies of about zero. Thermal treatments, such as He at 623 K, changed the conversion-temperature characteristics to the well-known S-shape, with activation energies slightly below 30 kJ mol(-1). Sample characterization by XAFS and electron microscopy and a low-temperature IR study of CO adsorption and oxidation showed that CO can be oxidized by gas-phase O2 at 90 K already over the freeze-dried catalyst in the initial state that contained Au exclusively in the +3 oxidation state. CO conversion after activation in the feed at 303 K is due to Au(III)-containing sites at low temperatures, while Au(0) dominates conversion at higher temperatures. After thermal treatments, CO conversion in the whole investigated temperature range results from sites containing exclusively Au(0).
authors.affiliation: Lehrstuhl Technische Chemie, Ruhr-Universität Bochum, P.O. Box 102148, 44780 Bochum (Germany). w.gruenert@techem.rub.de.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Grünert
authors.forename: Dennis
authors.initials: D
authors.lastname: Großmann
authors.forename: Heshmat
authors.initials: H
authors.lastname: Noei
authors.forename: Marga-Martina
authors.initials: MM
authors.lastname: Pohl
authors.forename: Ilya
authors.initials: I
authors.lastname: Sinev
authors.forename: Andrea
authors.initials: A
authors.lastname: De Toni
authors.forename: Yuemin
authors.initials: Y
authors.lastname: Wang
authors.forename: Martin
authors.initials: M
authors.lastname: Muhler
keywords: CO oxidation; active sites; gold; spectroscopy; titanium dioxide