J. Phys. Colloques 47 (1986) C8-273-C8-276
TEMPERATURE DEPENDENCE OF THE Pt L3-EDGE EXAFS OF PLATINUM CLUSTERS SUPPORTED ON NaY-ZEOLITET. YOKOYAMA, N. KOSUGI, K. ASAKURA, Y. IWASAWA et H. KURODA
Department of Chemistry, Faculty of Science, The University of Tokyo, Hongo, Tokyo 113, Japan
The temperature dependence of the Pt L3-edge EXAFS spectra of the platinum clusters encaged in the cavities of the NaY-zeolite were observed by use of synchrotron radiation. A contraction of Pt-Pt bond by 0.07 Å from the distance in the bulk Pt metal is observed, which is likely to be associated with a strong electron deficiency of the platinum clusters. The temperature dependence of the mean square relative displacement (MSRD) shows that the static disorder in this system is large, while the thermal disorder is significantly smaller than that of the bulk metal. The estimated Debye temperature is 310 K, which is much higher than that of the bulk metal (240 K). This unusual phenomenom seems to be associated with the increase of the binding energy between platinum atoms and with the strong interaction between a cluster and zeolite-framework (the cage effect).