Mesoporous Microspheres Composed of PtRu Alloy

Mesoporous microspheres of PtRu alloy have been successfully prepared by the electrochemical co-reduction of dihydrogen hexachloroplatinate(IV) and ruthenium trichloride both dissolved in the aqueous domains of the liquid crystalline phase of an oligoethylene oxide surfactant. Scanning electron micrographs reveal that the microspheres have a narrow size distribution in the range 0.5-1 µm. The ordered mesoporous internal structure of the microspheres has been confirmed by transmission electron micrographs and is characterized by periodic pores of ca. 2.4 nm in diameter separated by walls of ca. 2.4 nm thick. X-ray diffraction studies show that a higher Ru content is alloyed in the material than typically found in chemically prepared PtRu catalysts. The specific electrochemical surface area measured using both the CO adsorption and underpotential deposited Cu stripping techniques is 78-81 m2g-1-much larger than that of unsupported precious metal catalysts produced using standard techniques. The combination of high surface area and periodic nanostructure of this alloy material makes it an interesting prospective fuel cell electrocatalyst. This has been demonstrated by the high activity of the electrodeposited mesoporous PtRu material toward methanol electrooxidation.