Influence of the reduction temperature on the structure of the metal particles and the metal-support interface of Pt/γ-Al2O3 catalysts
| Autor: | M Vaarkamp, DC Diek Koningsberger |
|---|---|
| Rok vydání: | 1995 |
| Předmět: |
Materials science
Hydrogen chemistry.chemical_element Scheikunde Condensed Matter Physics Electronic Optical and Magnetic Materials Catalysis Amorphous solid Metal Transition metal Chemical engineering chemistry visual_art visual_art.visual_art_medium Cluster (physics) Particle size Electrical and Electronic Engineering Platinum |
| Zdroj: | Physica B, condensed matter, 208-209(1-4), 633. Elsevier |
| ISSN: | 0921-4526 |
| DOI: | 10.1016/0921-4526(94)00776-r |
| Popis: | The structure of the metal particles and the metal-support interface of a Pt@c-Al{2}O{3} catalyst was determined by EXAFS after low temperature reduction (LTR: 300}o{ C) and high temperature reduction (HTR: 450}o{ C). The clusters have excellent thermal stability as the particle size remains 12 atoms per cluster upon increasing the reduction temperature from 300}o{ C to 450}o{ C. However, the structure of the metal-support interface is a strong function of the reduction temperature. After LTR and in the presence of chemisorbed hydrogen the metal particles are at a distance of 2.68 a from the support oxygen ions. This long Pt-O distance is due to the presence of hydrogen between the platinum atoms and the support. Increasing the reduction temperature results in the removal of hydrogen from the metal-support interface, simultaneously placing the metal particles in direct contact with the support oxygen atoms at a distance of 2.28 a. The release of interfacial hydrogen during high temperature reduction is changing the metal-support interaction, which in turn changes the electron density distribution in the metal particles. The electronic and thereby the catalytic properties of the platinum metal particles are therefore a function of the reduction temperature. The results show that the influence of the reduction temperature on the structure of the metal-support interface of platinum particles on a amorphous support is similar to platinum particles which reside in cavities of zeolites. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Full Text from ScienceDirect