التفاصيل البيبلوغرافية
| العنوان: |
CO adsorption and desorption on size-selected Pdn/TiO2(110) model catalysts: Size dependence of binding sites and energies, and support-mediated adsorption. |
| المؤلفون: |
Kaden, William E.1, Kunkel, William A.1, Roberts, F. Sloan1, Kane, Matthew1, Anderson, Scott L.1 |
| المصدر: |
Journal of Chemical Physics. 5/28/2012, Vol. 136 Issue 20, p204705. 12p. 6 Graphs. |
| مصطلحات موضوعية: |
*ADSORPTION (Chemistry), *TEMPERATURE effect, *HELIUM ions, *CARBON monoxide, *TITANIUM catalysts, *BINDING energy, *X-ray photoelectron spectroscopy |
| مستخلص: |
The nature of CO adsorption on Pdn/TiO2(110) (n = 1, 2, 7, 20) has been examined using temperature-programmed desorption (TPD), temperature-dependent helium ion scattering (TD-ISS), and X-ray photoelectron spectroscopy (XPS). All samples contain the same number of Pd atoms (0.10 ML-equivalent) deposited as different size clusters. The TPD and TD-ISS show that CO binds in two types of sites associated with the Pd clusters. The most stable sites are on top of the Pd clusters ('on-top' sites), however, there are also less stable sites, in which CO is bound in association with, but not on top of the Pd ('peripheral' sites). For saturation CO coverage over a fixed atomic concentration of Pd (present in the form of Pdn clusters of varying size), the population of CO in peripheral sites decreases with increasing cluster size, while the on-top site population is size-independent. This is consistent with what geometric considerations would predict for the density of the two types of sites, provided the clusters adsorb predominantly as 2D islands, which ISS results suggest to be the case. The XPS analysis indicates that CO-Pd binding is dominated by π-backbonding to the Pdn clusters. The results also show evidence for efficient support-mediated adsorption (reverse-spillover) of CO initially impinging on TiO2 to binding sites associated with the Pd clusters. [ABSTRACT FROM AUTHOR] |
| قاعدة البيانات: |
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