Cluster Chemistry: Size-Dependent Reactivity Induced by Reverse Spill-Over
| Autor: | Ken Judai, Matthias Arenz, Stéphane Abbet, Martin A. Röttgen, Anke S. Wörz, Ulrich Heiz, Claude R. Henry, Jean-Marie Antonietti |
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| Rok vydání: | 2007 |
| Předmět: |
Chemistry
Cluster chemistry Analytical chemistry Flux 02 engineering and technology General Chemistry 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences Biochemistry Catalysis 0104 chemical sciences Reaction rate Colloid and Surface Chemistry Cluster (physics) Reactivity (chemistry) Diffusion (business) 0210 nano-technology Molecular beam |
| Zdroj: | Journal of the American Chemical Society. 129:9635-9639 |
| ISSN: | 1520-5126 0002-7863 |
| DOI: | 10.1021/ja068437f |
| Popis: | In the present work, the CO oxidation rate on size-selected Pd clusters supported on thin MgO films is investigated in pulsed molecular beam experiments. By varying the cluster coverage independent of the cluster size, we were able to change the ratio of direct and diffusion flux (reverse spill-over) of CO onto the cluster catalyst and thus probe the influence of reverse spill-over on the reaction rate for different cluster sizes (Pd(8) and Pd(30)). The experimental results show that the change in reaction rate as a function of cluster coverage is different for Pd(8) and Pd(30). In order to explain these findings, the CO flux onto the clusters is modeled utilizing the collection zone model for the given experimental conditions. The results indicate that, for small clusters (Pd(8)), the reaction probability of an impinging CO molecule is independent of whether it is supplied by diffusion or direct flux. By contrast, for larger clusters (Pd(30)) a reduced reaction probability is found for CO supplied by reverse spill-over compared to CO supplied by direct flux. |
| Databáze: | OpenAIRE |
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