| Research Abstract |
Metal thin films (Ni,Pd,Pt,Ru) and their borides and phosphides were prepared by using the RF sputtering method. Amorphous alloy thin films with various compositions were easily prepared by changing the sputtering conditions. In the metal boride films, boron donated electrons to metal, resulting in the high electron density of metal. With the metal phosphide films, phosphorous accepted electrons from metal, resulting in the low electron density of metal. In the hydrogenation of diolefins (1,3-butadiene and cyclopentadiene) and acetylene over these alloy thin films, the selectivity for the partial hydrogenation was explained in terms of the ensemble and the ligand effects. The small ensemble size and the low electron density of metal brought about the high selectivity for the partial hydrogenation. Especially, amorphous Pd_<75>P_<25> film showed the high selectivity (>95%) and further Pd_<75>P_<25> film heated in a vacuum, which was crystallized, exhibited the higher selectivity (>99%). On the other hand, the structure dependence in the hydrogenation of diolefins and acetylene was investigated on the Ru and Pd films. The orientation of the crystal faces changed with the film growth, that is, the orientation altered from (002) orientation to (101) orientation in the Ru films while changed from (111) orientation to (220) orientation in the Pd film. It was found that the (002) oriented Ru film and the (220) oriented Pd film showed the high selectivity for the hydrogenation. These metal films had the columnar structure and therefore the surface area of the films increased with the film growh. The active and selective film catalysts were developed by using the RF sputtering method.
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