Fine-tuning the dispersion and the mobility of BaO domains on NO x storage materials via TiO2 anchoring sites
Author
Andonova, S. M.
Şentürk, G. S.
Ozensoy, E.
Date
2010Source Title
Journal of Physical Chemistry C
Print ISSN
1932-7447 (print)
Publisher
American Chemical Society
Volume
114
Issue
40
Pages
17003 - 17016
Language
English
Type
ArticleItem Usage Stats
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Abstract
In an attempt to control the surface dispersion and the mobility of BaO domains on NOx storage materials, TiO2/TiOx anchoring sites were introduced on/inside the conventional γ-Al 2O3 support matrix. BaO/TiO2/Al 2O3 ternary oxide materials were synthesized via two different sol-gel preparation techniques, with varying surface compositions and morphologies. The synthesized NOx storage materials were studied via XRD, Raman spectroscopy, BET surface area analysis, TPD, XPS, SEM, EDX-mapping, and in situ FTIR spectroscopy of adsorbed NO2. NOx uptake properties of the BaO/TiO2/Al2O3 materials were found to be strongly influenced by the morphology and the surface structure of the TiO2/TiOx domains. An improved Ba surface dispersion was observed for the BaO/TiO2/Al2O3 materials synthesized via the coprecipitation of alkoxide precursors, which was found to originate mostly from the increased fraction of accessible TiO 2/TiOx sites on the surface. These TiO2/ TiOx sites function as strong anchoring sites for surface BaO domains and can be tailored to enhance surface dispersion of BaO. TPD experiments suggested the presence of at least two different types of NOx species adsorbed on the TiO2/TiOx sites, with distinctively different thermal stabilities. The relative stability of the NOx species adsorbed on the BaO/TiO2/Al2O3 system was found to increase in the following order: NO+/N2O 3 on alumina ≪ nitrates on alumina < surface nitrates on BaO < bridged/bidentate nitrates on large/isolated TiO2 clusters < bulk nitrates on BaO on alumina surface and bridged/bidentate nitrates on TiO2 crystallites homogenously distributed on the surface < bulk nitrates on the BaO sites located on the TiO2 domains. © 2010 American Chemical Society.
Keywords
Alkoxide precursorAlumina surface
BET surface area
EDX-mapping
In-situ FT-IR
Relative stabilities
SEM
Sol gel preparations
Support matrix
Surface compositions
Surface dispersion
Surface nitrates
Ternary oxide material
Thermal stability
TiO
Uptake properties
XPS
XRD
Aluminum
Barium
Dispersions
Fourier transform infrared spectroscopy
Materials
Morphology
Nitrates
Raman spectroscopy
Surface morphology
Surfaces
Permalink
http://hdl.handle.net/11693/22176Published Version (Please cite this version)
https://doi.org/10.1021/jp102555cCollections
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