Structure of bimetallic clusters. Extended xhyphen;ray absorption fine structure (EXAFS) studies of Irndash;Rh clusters

摘要

The extended xhyphen;ray absorption fine structures (EXAFS) associated with theLIIIabsorption edge of iridium and theKabsorption edge of rhodium were investigated for catalysts containing bimetallic clusters of these elements dispersed on silica or alumina. The catalysts contained 1 wt.percnt; iridium and 0.5 wt.percnt; rhodium, which corresponds to an Ir/Rh atomic ratio close to 1. From the EXAFS data, it is concluded that the rhodium concentration in the surface region of the iridiumndash;rhodium clusters is greater than it is in the interior. The EXAFS data also indicate that the iridiumndash;rhodium clusters are more highly dispersed on alumina than on silica.