Acetylene trimerization on Ag, Pd and Rh atoms deposited on MgO thin films
| Autor: | Gianfranco Pacchioni, Stéphane Abbet, Ken Judai, Livia Giordano, Anke S. Wörz, Annalisa Del Vitto, Ueli Heiz, Jean-Marie Antonietti |
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| Přispěvatelé: | Judai, K, Worz, A, Abbet, S, Antonietti, J, Heiz, U, DEL VITTO, A, Giordano, L, Pacchioni, G |
| Rok vydání: | 2005 |
| Předmět: |
Steric effects
Inorganic chemistry General Physics and Astronomy Atmospheric temperature range Metal chemistry.chemical_compound Crystallography Acetylene chemistry Transition metal Vacancy defect visual_art Atom visual_art.visual_art_medium oxide surfaces DFT Electron configuration Physical and Theoretical Chemistry |
| Zdroj: | Phys. Chem. Chem. Phys.. 7:955-962 |
| ISSN: | 1463-9084 1463-9076 |
| DOI: | 10.1039/b414399j |
| Popis: | The acetylene trimerization on the group VIII transition metal atoms, Rh and Pd, as well as on Ag atoms supported on MgO thin films has been studied experimentally and theoretically. The three metal atoms with the atomic configurations 4d(8)5s(1) (Rh), 4d(10)s(0) (Pd) and 4d(10)5s(1)(Ag) behave distinctly differently. The coinage metal atom silver is basically inert for this reaction, whereas Pd is active at 220 and 320 K, and Rh produces benzene in a rather broad temperature range from 350 to ca. 430 K. The origins of these differences are not only the different electronic configurations, leading to a weak interaction of acetylene with silver due to strong Pauli repulsion with the 5s electron but also the different stability and dynamics of the three atoms on the MgO surface. In particular, Rh and Pd atoms interact differently with surface defects like the oxygen vacancies (F centers) and the step edges. Pd atoms migrate already at low temperature exclusively to F centers where the cyclotrimerization is efficiently promoted. The Rh atoms on the other hand are not only trapped on F centers but also at step edges up to about 300 K. Interestingly, only Rh atoms on F centers catalyze the trimerization reaction whereas they are turned inert on the step edges due to strong steric effects. |
| Databáze: | OpenAIRE |
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