Martin McBriarty
Dept of Materials Science and Engineering
Northwestern University

Chemically Reactive Oxide Surfaces: An In Situ Atomic-Scale View

Location: EB1 Room 1011

Friday, May 9th 2014 - 11:00 am

Oxide catalysts are integral to chemical production, fuel refining, and the removal of environmental pollutants. However, the atomic-scale phenomena which lead to the useful reactive properties of catalyst materials are not sufficiently understood. We use the tools of surface and interface science to investigate the structure and chemical properties of catalytically active particles and ultrathin films supported on oxide single crystals. In situ synchrotron X-ray measurements are sensitive to changes in the atomic-scale geometry of these model catalyst surfaces through chemical reaction cycles, while X-ray spectroscopy reveals corresponding oxidation state shifts. Experimental results are bolstered by theoretical calculations of surface structures, allowing for detailed predictions of surface chemical phenomena. Our work focuses on the structure-property relationships in vanadium oxide, tungsten oxide, and mixed V-W oxides grown on Al2O3, Fe2O3, and TiO2 single crystal substrates by atomic layer deposition. The surface configurations and oxidation states of V and W are found to depend on the coverage of each, and reversible structural shifts accompany chemical state changes through reduction-oxidation cycles. Substrate-dependent effects suggest how the choice of oxide support material may affect catalytic behavior. These studies of catalytically active material surfaces can inform the rational design of new catalysts for more efficient and sustainable chemistry.

North Carolina State University