Autor: James A. Dumesic, Randy D. Cortright, Ramchandra M. Watwe, B. E. Spiewak
Rok vydání: 1998
Předmět:
Zdroj: Catalysis Letters. 51:139-147
ISSN: 1011-372X
DOI: 10.1023/a:1019038512945
Popis: Microcalorimetric measurements were conducted at 573 K of CO adsorption on Pt clusters supported in L-zeolite. The measured heat of CO adsorption is 175 kJ/mol, and the heat decreases to 90 kJ/mol near saturation coverage. Quantum chemical calculations were performed using density functional theory to study the interaction of CO with 10-atom Pt clusters. The heat of CO adsorption on atop-sites is calculated to be 209 kJ/mol, while a lower heat of 142 kJ/mol is calculated for CO on bridge-sites. These values decrease to 197 and 102 kJ/mol for population of two atop-sites and two bridge-sites, respectively, on the same Pt10 cluster. The heat of adsorption decreases to 157 kJ/mol when six CO molecules adsorb on six atop-sites of the cluster. The calculated initial heat of CO adsorption on Pt10 clusters is in agreement with experimental and theoretical values reported for CO adsorption on Pt single-crystal surfaces. The higher heat of CO adsorption at atop-sites may be caused by more σ-donation from CO to sp orbitals of Pt for atop-sites. The heat of CO adsorption on bridge-sites becomes higher on negatively charged platinum clusters. The calculated C-O stretching frequencies for charged and neutral platinum clusters agree with experimental data.
Databáze: OpenAIRE
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