Abstract
A combination of in-situ electron microscopy and surface chemical techniques (XPS, EELS) has been used to study the interaction of platinum particles with a support of mixtures of thin films of titanium oxide and graphite when treated in hydrogen. The morphological characteristics exhibited by the metal particles were strongly dependent on the location of the particles on this composite support. At temperatures near 500/sup 0/C the titanium oxide film rearranged into hexagonal-shaped islands and dendrites. Platinum particles, located on these titania regions transformed from dense globules to thin, flat structures and remained in this form up to elevated temperatures. In contrast, the metal particles on the graphite maintained their globular morphology at all temperatures; however, they subsequently exhibited two distinct patterns of behavior, depending on their proximity to titania. Two types of particles were active in catalyzing the hydrogenation of graphite, kinetic analysis showed that the intrinsic channeling rate of Pt-TiO/sub 2/ particles was three orders of magnitude faster than that of Pt particles at 1000/sup 0/PC. Consistent with these data is the finding from surface chemical analysis that a new phase is formed when Pt/TiO/sub 2//graphite specimens were treated in hydrogen at 800/sup 0/C. 22 references, 7 figures, 1more » table.« less
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