Structure of supported PdAu clusters determined by X-ray absorption spectroscopy
- Stanford Univ., CA (United States)
The extended X-ray absorption fine structure (EXAFS) above the Pd K and Au L[sub III] edges and the X-ray absorption near edge structure (XANES) associated with the Au L[sub III] edge were used to study the structure and local electronic environment of PdAu bimetallic clusters supported on silica. Four samples with total metal loadings of approximately 100 [mu]mol g[sup [minus]1] and varying PdAu compositions were investigated. Transmission electron microscopy performed on a bimetallic sample (Pd:Au mole ratio equal to 60:40) exposed to air failed to detect any metal particles, indicating that their average diameter was less than 1 nm, which corresponds to [approximately] 100% metal exposed. The EXAFS for bimetallic clusters (Pd:Au = 60:40) in vacuum at 77 K shows that Pd atoms decorate a core of Au atoms. The Pd-Pd interatomic distance in the bimetallic sample is the same as in bulk Pd, whereas the Au-Au interatomic distance is 3% shorter than that in bulk Au. The XANES associated with the Au L[sub III] edge indicates that Au has an atomic-like electronic structure when alloyed with Pd, which is due to Au atoms having fewer like nearest neighbors in the clusters compared to bulk Au. 38 refs., 8 figs., 3 tabs.
- DOE Contract Number:
- AC03-82ER13000; AC02-76CH00016
- OSTI ID:
- 7073148
- Journal Information:
- Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 98:21; ISSN JPCHAX; ISSN 0022-3654
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360101 -- Metals & Alloys-- Preparation & Fabrication
360102* -- Metals & Alloys-- Structure & Phase Studies
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102 -- Chemical & Spectral Procedures
ABSORPTION SPECTROSCOPY
ADSORPTION
AMMONIA
CATALYST SUPPORTS
CHALCOGENIDES
DATA
ELECTRON MICROSCOPY
ELEMENTS
EXPERIMENTAL DATA
GOLD
HYDRIDES
HYDROGEN COMPOUNDS
INFORMATION
METALS
MICROSCOPY
MINERALS
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NONMETALS
NUMERICAL DATA
OXIDE MINERALS
OXIDES
OXYGEN
OXYGEN COMPOUNDS
PALLADIUM
PLATINUM METALS
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SOLID CLUSTERS
SORPTION
SPECTROSCOPY
TRANSITION ELEMENTS
TRANSMISSION ELECTRON MICROSCOPY
X-RAY SPECTROSCOPY