Inelastic electron tunneling spectroscopy of a model catalyst: CO on Rh/Al2O3 |
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| Affiliation: | 1. Sustainable Energy Laboratory, Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan, 430073, China;2. National Research University “Moscow Power Engineering Institute”, 14, Krasnokazarmennaya St., 111250 Moscow, Russia;3. National Research Centre “Kurchatov Institute”, 1, Kurchatov Sq., 123182 Moscow, Russia;1. Department of Science and Agroforestry Technology and Genetics, Higher Technical School of Agricultural and Forestry Engineering, University of Castilla-La Mancha, Campus Universitario s/n, CP 02071, Albacete, Spain;2. Department of Applied Physics, School of Industrial Engineering, University of Castilla-La Mancha, Campus Universitario s/n, CP 02071, Albacete, Spain;3. Environmental Department, Renewable Energy Research Institute, University of Castilla-La Mancha, Campus Universitario s/n, CP 02071, Albacete, Spain;1. College of Chemistry and Materials Science, Center for Nano Science and Technology, Anhui Normal University, Wuhu 241000, China;2. Nanomaterials and Environment Detection Laboratory, Institute of Intelligent Machines, Chinese Academy of Sciences, Hefei 230031, China;3. Department of Mechanical and Automotive Engineering, Anhui Polytechnic University, Wuhu 241000, China;1. Department of Chemical and Environmental Engineering, University of Oviedo, Faculty of Chemistry, Julián Clavería s/n, 33006 Oviedo, Spain;2. AXES Research Group, Department of Chemistry, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium |
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| Abstract: | Using tunneling spectroscopy we have studied the preparation and behavior of dispersed rhodium model catalysts supported on alumina. Samples were prepared by vacuum evaporation from Rh metal or Rh2O3 sources onto an oxidized Al film and CO was adsorbed in-situ. The tunnel junctions were formed by adding a Pb top electrode and the vibrational spectra of the adsorbed species were measured. We observed qualitatively different spectra when the preparation procedure was varied. Special care was taken to monitor and control background gases. We obtained different results from Rh of Rh2O3 sources and the presence of oxygen or water affects the vibrational spectra of the adsorbed CO. We also study the effect of the Rh thickness on the spectral intensity. Other experiments were measurement of the superconducting tunneling spectra of the Pb and a TEM study of Rh particle size. Previously reported data from tunneling and IR measurements are compared with the present work. Based on these results, we conclude that there are two species present, either a linear Rh-CO or doubly (geminal) adsorbed Rh(CO)2 depending upon the degree of dispersion and oxidation of the Rh. The evidence also indicates that in both instances a dispersed form of Rh, rather than relatively large Rh metal particles, is responsible for the observed spectra. |
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