Au−Pd Nanoparticles Dispersed on Composite Titania/Graphene Oxide-Supports as a Highly Active Oxidation Catalyst

The control over both the dispersion and the particle size distribution of supported precious metal nanoparticles used in heterogeneous catalysts is of paramount importance. Here, we demonstrate the successful formation of highly accessible and well dispersed gold−palladium nanoparticles, stabilized with two-dimensional graphene oxide, that itself is dispersed by intercalated titania particles to form ternary hybrid catalysts. In this application, graphene oxide acts as an effective substitute for the more conventional polymer ligands that are used to stabilize nanoparticles in a sol-immobilization procedure. The particle size distribution can be adjusted by varying the graphene oxide-tometal mass ratio. The addition of titania efficiently hinders the stacking and agglomeration of the supported metal on graphene oxide sheets, facilitating diffusion of oxygen and reactants to the catalyst surface. This gold−palladium/graphene oxide/titania “ternary” catalyst has been tested for the selective oxidation of a range of alcohols. The resulting optimized catalyst exhibits a comparable activity to a solimmobilized derived catalyst where the metal nanoparticles are stabilized by poly(vinyl alcohol) ligands, with the graphene oxidestabilized hybrid catalyst having enhanced stability. We consider that the novel strategy of supporting metal nanoparticles described here can also be adopted to synthesize a wide range of high activity, stable heterogeneous catalysts for other reactions.