In:
Journal of Materials Research, Springer Science and Business Media LLC, Vol. 12, No. 5 ( 1997-05), p. 1376-1384
Abstract:
Rh nanoparticles supported on ZrO 2 powder were prepared by adsorbing Rh 4 (CO) 12 clusters from hexane solution under Ar atmosphere. Four samples with Rh content ranging from 0.25 Rh wt.% up to 4.10 Rh wt.% were studied by x-ray diffraction (XRD), transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), scanning Auger microscopy (SAM), and time of flight secondary ion mass spectroscopy (ToF-SIMS). TEM measurements show, for all the samples, Rh particles with a size of about 50 Å. The 4.10 Rh wt.% sample also shows some agglomerates of Rh nanoparticles and only for this sample Rh metallic phase was detected by XRD. The profile analysis of the XRD lines indicates an average size of the Rh crystallites of about 60 Å. XPS studies show only a single spectral component for the Zr 3 d 5/2 core line at 182.2 eV. Instead, at least, two components at 307.2 eV and 308.5 eV are detected for the Rh 3 d 5/2 core line. These results suggest that Zr is present only as oxidized state, whereas nonoxidized and oxidized Rh are both observed. A nonoxidized Rh state is also suggested by the XPS valence band electron removal spectrum which exhibits a significant emission within the ZrO 2 band gap assigned to Rh 4 d bands. A further support to this finding arises from scanning Auger maps of O KVV and RH where nonoxidized Rh is observed. Finally scanning Auger maps using the O KVV and the Zr emissions show surface regions where only the Zr Auger lines are detected, whereas on pure ZrO 2 powder this effect is not observed. Since it is possible to rule out from the XPS Zr 3 d core line spectra, the presence of metallic zirconium hydrogen spillover mechanisms is invoked to explain this result.
Type of Medium:
Online Resource
ISSN:
0884-2914
,
2044-5326
DOI:
10.1557/JMR.1997.0187
Language:
English
Publisher:
Springer Science and Business Media LLC
Publication Date:
1997
detail.hit.zdb_id:
54876-5
detail.hit.zdb_id:
2015297-8
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