Small metal clusters on metal oxides have the potential of being excellent catalytic sites. The group is able to exploit its knowledge of synthesis and surface chemistry to produce doped and/or decorated metal oxides to study surface catalysis. We are able to decorate our metal oxides with nickel, palladium, tin oxide, gold, and other metals through the same patented process that we use to synthesize MgO, and also through a second, solution-based chemical process. The photo album at left includes images of silica spheres decorated with tin oxide, gold, and palladium, nickel-doped MgO, and palladium-decorated ZnO and MgO.
Materials such as ZnO, MgO and various forms of silica have been doped with coinage metals and studied for catalytic activity. Among the forms of silica being studied, high surface area materials such as SBA-15 and hollow mesoporous silica spheres have been decorated with coinage metal nanoparticles to be used as heterogeneous catalysts. Specific reactions under investigation include Heck coupling reactions, the selective hydrogenation of allyl alcohol, and hydrogen peroxide formation. One current research topic is the use of a chelating bio-polymer as a coating/transport agent inside the pores of the silica materials and its effectiveness in reducing the leaching of palladium. Characterization of the materials is performed by ICP-OES, FTIR, TEM, adsorption/desorption isotherms, XPS and SAXS.
Another use of the silica materials may be as a template for nanostructures. Currently a novel synthetic route to gold and palladium nanowires is under investigation using SBA-15 as a template. Using the same chelating agent, it was found that a simple thermal treatment could be used to produce wires of 200 to 500 nm and ~7 nm in diameter within the silica pore channels. These materials are under investigation by high-resolution TEM, XPS, and adsorption/desorption isotherms.