COMBINED XANES AND EXAFS ANALYSIS OF SUPPORTED BIMETALLIC CATALYSTS

EXAFS has been used for many years to characterise the structure of bi metallic catalysts. In the majority of these it is assumed that all of the metal components are present as the bimetallic system, either a s egregated metal particle or intermit alloy. In this study we report a combined XANES/EXAFS method for determining both the degree of alloy f ormation and the structure of the bimetallic metal particles formed. U sing a quantitative analysis of the X-ray absorption spectra of a rang e of standard Pd/Au alloy foils, as well as supported catalysts. It is shown that the catalysts consisted of fully mixed Pd/Au alloy, free P d and free Au particles. The relative proportion of each component bei ng dependent the relative proportions of Pd and Au used in the catalys ts preparation.