Synthesis of Cluster-Derived PtFe/SiO(2) Catalysts for the Oxidation of CO
Infrared (FTIR) and extended X-ray absorption fine structure (EXAFS) spectroscopy measurements were used to characterize the species formed after impregnation of Pt{sub 5}Fe{sub 2}(COD){sub 2}(CO){sub 12} onto silica, before and after removal of the organic ligands. The results indicate that the Pt{sub 5}Fe{sub 2}(COD){sub 2}(CO){sub 12} cluster adsorbs weakly on the SiO{sub 2} surface. Nevertheless, partial disintegration of the cluster was observed during aging even under He and at room temperature, related to the loss of CO ligands due to their interactions with silanol groups of the support. The organic ligands can be removed from a freshly impregnated cluster by thermal treatment in either He or H{sub 2}, but the surface species formed in each case have different structures. Treatment in He at 350 {sup o}C leads to a complete disintegration of the Pt-Fe bimetallic core and results in the formation of highly dispersed Pt clusters with a nuclearity of six, along with surface Fe oxide-like species. In contrast, bimetallic PtFe nanoparticles with an average size of approximately 1 nm were formed when a similar H{sub 2} treatment was used. In this case, a greater degree of metal dispersion and a larger fraction of Pt-Fe interactions were observed compared to the PtFe/SiO{sub 2} samples prepared by co-impregnation of monometallic salt precursors. Electronic interactions between Pt and Fe atoms in such cluster-derived samples led to an increased electron density on platinum, as indicated by a red shift of the frequencies of FTIR bands for adsorbed NO and CO. These electronic interactions affect the strength of the CO adsorption on platinum. All bimetallic samples were found to be more active than Pt/SiO{sub 2} for the oxidation of CO in air; however, the activity depends strongly on the structure of the surface species, the fraction of Pt-Fe bimetallic contributions, the degree of electronic interactions between Pt and Fe, and the strength of the CO adsorption on platinum.
- Research Organization:
- SLAC National Accelerator Lab., Menlo Park, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC02-76SF00515
- OSTI ID:
- 953562
- Report Number(s):
- SLAC-REPRINT-2009-321; JCTLA5; TRN: US201002%%1390
- Journal Information:
- J. Cat. 255:162,2008, Vol. 255, Issue 2; ISSN 0021-9517
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ABSORPTION
ABSORPTION SPECTROSCOPY
ADSORPTION
AGING
AIR
ATOMS
CATALYSTS
DISPERSIONS
ELECTRON DENSITY
FINE STRUCTURE
HETEROGENEOUS CATALYSIS
INTERACTIONS
IRON
LIGANDS
METALS
OXIDATION
PLATINUM
POLYTETRAFLUOROETHYLENE
RED SHIFT
REMOVAL
SALTS
SILICA
SILICON OXIDES
SIZE
SPECTROSCOPY
SURFACES
SYNTHESIS
TRANSITION ELEMENTS
Other
OTHER