Structure of bimetallic clusters. Extended xhyphen;ray absorption fine structure (EXAFS) of Ptndash;Re and Pdndash;Re clusters

摘要

Extended xhyphen;ray absorption fine structure (EXAFS) studies were conducted on catalysts containing platinum and rhenium, or palladium and rhenium, on alumina. The atomic ratio of rhenium to either platinum or palladium was close to one in the catalysts investigated. The metallic entities in the catalysts were characterized by analyses of the EXAFS associated with theLIabsorption edge of platinum, theLIIIedge of rhenium, and theKabsorption edge of palladium. It was concluded that Ptndash;Re and Pdndash;Re bimetallic clusters are present in the catalysts. However, the clusters have regions rich in rhenium and other regions which are rich in either platinum or palladium. Exposure of Ptndash;Re clusters to sulfur has little influence on their structure.