Atomically Resolved Studies of Transition Metal Oxides
EMSL Project ID
7192
Abstract
STM and AFM studies will be conducted on surfaces of small crystalline domains and epitaxially grown thin TMO films such as γ-WO3(001), TiO2(110), and V2O5/TiO2(110). Such studies give detailed structural information about the extended TMO surfaces, about their reconstruction, and about the type and density of steps and oxygen vacancies, implicated in the catalytic reactivity of metal oxides. Preferential adsorption sites can be determined by imaging the sample prior to and after adsorption of the molecule of interest in-situ so the same area of the substrate is imaged. Adsorbates include reactants (e.g., C3H8, CH3OH, O2) and products (e.g., C3H6, CH2O, H2O) of the catalytic reactions targeted in this proposal.Thermally-induced changes in the adsorbate-covered TMO surfaces will be followed using time-lapse imaging during temperature ramping. These studies will provide essential information about local formation rates of reaction intermediates and products at various regions of the substrate. These temporally-and spatially-resolved studies will be compared with ensemble-averaged kinetic studies using molecular beam and thermal desorption techniques.
We will also use STM/AFM to probe the nature of the sites on the substrate acting as nucleation centers for TMO cluster growth. The size and spatial distribution of the TMO clusters will be studied as a function of growth conditions in order to correlate structure with reactivity. Size-dependent changes in the electronic structure of the TMO clusters will be determined using STS analogous to previous studies of metal clusters on oxide surfaces. This information is required in order to understand the cluster size dependent chemical activity for such TMO clusters. After these growth studies, the reactivity of the clusters will be examined using STM/AFM as outlined above for extended TMO surface studies. The structure and reactivity of the supported TMO clusters will be compared with those of the extended TMO surfaces. These comparisons will enable us to elucidate the origin of the enhanced chemical activity of supported clusters relative to extended surfaces.
Project Details
Project type
Exploratory Research
Start Date
2004-02-16
End Date
2006-01-22
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Bondarchuk O, X Huang, J Kim, BD Kay, LS Wang, JM White, and Z Dohnalek. 2006. "Formation of Monodisperse (WO3)3 Clusters on Ti02(110)." Angewandte Chemie International Edition 45(29):4786-4789.
Dohnalek Z, J Kim, O Bondarchuk, JM White, and BD Kay. 2006. "Physisorption of N2, O2, and CO on Fully Oxidized TiO2(110)." Journal of Physical Chemistry B 110(12):6229-6235.
Zhang Z, O Bondarchuk, JM White, BD Kay, and Z Dohnalek. 2006. "Imaging Adsorbate O-H Bond Cleavage: Methanol on TiO2(110)." Journal of the American Chemical Society 128(13):4198-4199.