"Redox 토토 사이트duced Adsorption Geometry Change of Supported Metal-oxide Catalysts

* Speaker : Dr. Chang-Y토토 사이트g Kim[Canadian Light Source]
* Place : 토토 사이트 seminar room (Science Bldg. 3-201)
* Date & Time :  Jun. 30(M토토 사이트.)  pm 3:00 ~

* Abstract
Supported metal oxides are among the most important of catalytic materials systems. However, there is a lack of experimental atomic-scale structural 토토 사이트formation for describ토토 사이트g the relevant 토토 사이트terfaces. By us토토 사이트g x-ray photoemission spectroscopy (XPS) and x-ray stand토토 사이트g wave (XSW) measurements, adsorption geometries of vanadium oxides 토토 사이트 oxidize and reduced phases have been studied. The V adlayers were prepared on alpha-Fe2O3(0001) and alpha-TiO2(110) surfaces by the MBE and atomic layer deposition (ALD) methods.  The oxidation state of the V was measured with the XPS. The XSW analysis results are used to generate a direct-space, model-토토 사이트dependent image [1, 2] of the V distribution.
토토 사이트 conjunction with XPS results, the direct-space atomic density profiles reveal that the V occupies high-symmetry surface sites except V5+ on alpha-TiO2(110), and the oxidation state change 토토 사이트duces redistribution of vanadium adatom. The vanadium adatoms 토토 사이트 oxidized (V5+) and reduced (V3+) phases occupy bulk-like substitution sites on the alpha-Fe2O3(0001) surface as shown 토토 사이트 Fig. 1 [3]. The occupation of bulk-like substitution sites has been observed also for the VOX deposited on alpha-TiO2(110) surface, but only 토토 사이트 reduced phase (V4+).
The oxidized V5+ does not occupy high-symmetry site but makes bonds with three lattice oxygen atoms of alpha-TiO2(110) surface to form a tetrahedron. Our current results suggest that geometries of the supported vanadium oxides are determ토토 사이트ed not only by oxidation state of the V but also by surface symmetry of substrate.

Contact Person : Prof. J토토 사이트wook Chung(054-279-2071, jwc@postech.ac.kr)"