AVS 52nd International Symposium
    Surface Science Wednesday Sessions
       Session SS2-WeM

Paper SS2-WeM8
Catalytic Activity of WO@sub 3@ Clusters on TiO@sub 2@(110): Trimerization of Formaldehyde

Wednesday, November 2, 2005, 10:40 am, Room 203

Session: Reactions on Metals & Oxides
Presenter: J. Kim, Pacific Northwest National Laboratory
Authors: J. Kim, Pacific Northwest National Laboratory
O.A. Bondarchuk, University of Texas, Austin
Z. Dohnálek, Pacific Northwest National Laboratory
J.M. White, University of Texas at Austin
B.D. Kay, Pacific Northwest National Laboratory
Correspondent: Click to Email
The catalytic activity of supported, high surface area transition metal oxides (TMO) catalysts have been extensively studied. In contrast, only a few studies have been conducted on transition metal oxide clusters supported on well-ordered, singe-crystalline oxide surfaces In this study, the catalytic activity of WO@sub 3@ clusters deposited on a well-characterized TiO@sub 2@(110) surface was examined. The clusters were deposited via direct, thermal evaporation of WO@sub 3@. This deposition technique provides a reliable, carbon free source of W in the (6+) oxidation state as shown by X-ray photoelectron spectroscopy (XPS). Related scanning tunneling microscopy (STM) studies reveal that 600 K-annealed WO@sub 3@ clusters are monodispersed and ~1 nm in diameter. Temperature programmed desorption (TPD) of N@sub 2@ reveals that the structure of WO@sub 3@ does not changed significantly between 400 - 600 K. We have examined the adsorption of formaldehyde (H@sub 2@CO) on TiO@sub 2@(110) and on WO@sub 3@ (< 4 x 10@super 14@ WO@sub 3@/cm@super -2@) on TiO@sub 2@(110). On TiO@sub 2@(110), H@sub 2@CO adsorbs and desorbs molecularly for all coverages. On WO@sub 3@/TiO@sub 2@(110), the adsorption of H@sub 2@CO multilayers results in the catalytic formation of trioxane. The trimerization yield increases with the amount of adsorbed H@sub 2@CO and saturates for coverages exceeding ~10 ML. Submonolayer coverage of H@sub 2@CO do not yield any trioxane product. The yield increases linearly with the amount of deposited WO@sub 3@ and the reaction can be run repeatedly. @FootnoteText@ *Pacific Northwest National Laboratory is operated for the Department of Energy by Battelle under Contract DE-AC06-76RLO 1830.