Ru-Co/NaY bimetallic catalysts: in situ EXAFS study at Co K- and Ru K-absorption edges
Résumé
In situ extended X-ray absorption fine structure (EXAFS) studies were performed on Ru-Co/NaY bimetallic samples in the “as received” state, in freshly reduced states, after being exposed to air, and on a “spent” catalyst. The Ru-Co/NaY catalyst gave no indication that Ru–Co bonds were formed, in contrast to earlier X-ray photoelectron spectroscopy (XPS) results. The metallic cobalt nanoparticles formed were somewhat larger than those of ruthenium. Even though bimetallic nanoparticles are not directly observed, it is plausible to suggest a model in which some cobalt nanoparticles are in intimate contact with ruthenium. Comparison of the freshly reduced and spent catalysts revealed that the size of cobalt particles increased only slightly while ruthenium interacted with light atoms (mainly carbon). The data are discussed in terms of the XPS and the CO hydrogenation results obtained earlier.