(736c) Investigation of Metal-Metal Oxide Support Interface

Although the interface between a support and metal nanoparticles is an integral component of all supported metal catalysts, there is little information on their properties. While direct measurement of these properties is challenging, we found it possible to gather relevant information using a model system in which an oxide ensemble of tunable composition that can be structured to mimic the interface is deposited on the metal particle. As an example, a system that mimics Au metal-support oxide interface is synthesized and examined for selective oxidation of propane, in which the proximity and the nuclearity of the support oxide ensemble can be varied. The synthesis of such catalytic system can be achieved in two ways.  In the first method, a poly-methylhydrosiloxane containing both Au precursor and metal oxo species of interest (for example Ti) are used to generate a composite. Following reduction of Au and removal of organics, Au next to Ti oxo clusters of low nuclearity is generated.  Another approach is to synthesize short oligomers of siloxane containing the metal-oxo species of interest in the center.  The two ends of the oligomers contain functionalities that will adsorb on Au nanoparticles.  The reactivities of these two types of catalysts in CO and propane oxidation are compared to gain better understanding of the active site structure.