Chemical States and Catalytic Properties of Icosahedral Al-Pd-Ru Quasicrystal and Its Approximants

The chemical states of Al71Pd19Ru10, an icosahedral Al-Pd-Ru quasicrystal, and of the approximants Al72Pd16.4Ru11.6 and Al70.4Pd14.7Ru14.9 were investigated using hard X-ray photoemission spectroscopy. Their catalytic properties for the hydrogenation of acetylene were also evaluated. Each of these Al-Pd-Ru alloys comprised mini-Bergman and pseudo-Mackay clusters but had varying structures as a consequence of differences in the arrangement of these clusters. The chemical states of the constituent elements and the acetylene hydrogenation characteristics were similar among these alloys. However, all three materials were significantly different from pure Pd, especially with regard to their chemical shift and performance during the semi-hydrogenation of acetylene. The catalytic activity of such alloys was found to be determined by the local surface structure rather than the crystal structure and/or the arrangement of the constituent clusters.