Investigation of the Structure of Platinum Clusters Supported in Zeolite Beta Using the Pair Distribution Function

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• 作者：Marí ; a M. Martí ; nez-I&ntilde ; esta ; Raú ; l F. Lobo
• 刊名：Journal of Physical Chemistry C
• 出版年：2007
• 出版时间：June 21, 2007
• 年：2007
• 卷：111
• 期：24
• 页码：8573 - 8579
• 全文大小：397K
• 年卷期：v.111,no.24(June 21, 2007)
• ISSN：1932-7455

文摘

Structural characterization of supported metal catalysts is a challenge because the metal clusters are small,usually polydisperse, and present in low loadings. Here, we describe the use of the pair distribution function(PDF) method to study the structure of platinum clusters supported in zeolite beta at a loading of 1.1% w/w.In addition to the characterization by the PDF method, the sample was characterized using X-ray diffraction,X-ray photoelectron spectroscopy, X-ray absorption, and dark-field scanning transmission electron microscopy.With these techniques, we were able to determine that the platinum clusters were in a reduced state,monodisperse, and located mainly in the pores. With the PDF technique, we were able to determine that thelocal structure of the clusters was similar to that of the bulk platinum. Contrary to what might be expected,the PDF results showed that the lattice parameters did not change significantly. However, attempts to modelthe PDF using a finite cluster with the bulk platinum structure did not yield quantitative agreement toexperiment, and it was determined that there were other interactions besides that of Pt-Pt affecting the PDF.Models that take into consideration different possible cluster shapes and sizes are necessary to completelydescribe the PDF at these low loadings. However, the PDF technique was shown to be valuable for theexperimental determination of the structure of supported nanoclusters.