Properties of Pd deposited on SiC(0001) single crystal surfaces

摘要

The catalytic properties of Pd deposited on SiC(0001) single crystals were examined. The SiC surface was prepared by ion bombardment and annealing, and characterised by AES, LEED, and XPS under UHV conditions. The surfaces obtained showed a carbon terminated surface, with a (1 x 1) LEED pattern. The model catalyst was obtained by vapodeposition of pure Pd. Three deposits were particularly studied corresponding respectively to 1.9 x 10(14), 5.4 x 10(14), and 2.9 x 10(15) Pd/cm(2). The Pd/SiC deposits were first characterised by AES, XPS, and tapping mode AFM. From quantitative treatment of the XPS data and analysis of AFM images (obtained "in air" on these surfaces after a reaction) one concludes that Pd particles are rather "flat." Moreover, Pd particles were found to retain some interaction with the SiC support leading to nearly a 1-eV higher energy of the Pd-3d5/2 level measured by XPS, as compared to massic Pd. Their catalytic properties were tested for the 1,3-butadiene hydrogenation reaction. The activities obtained, per Pd surface atom, range above those found for Pd surface atoms on pure Pd(111) and Pd(110). (C) 1998 Academic Press. [References: 24]