Water-induced morphology changes in BaO/γ-Al2O3 NOx storage materials: An FTIR, TPD, and time-resolved synchrotron XRD study

János Szanyi; Ja Hun Kwak; Do Heui Kim; Xianqin Wang; Ricardo Chimentao; Jonathan Hanson; William S. Epling; Charles H.F. Peden

doi:10.1021/jp067932v

Water-induced morphology changes in BaO/γ-Al₂O₃ NO_x storage materials: An FTIR, TPD, and time-resolved synchrotron XRD study

János Szanyi, Ja Hun Kwak, Do Heui Kim, Xianqin Wang, Ricardo Chimentao, Jonathan Hanson, William S. Epling, Charles H.F. Peden

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Abstract

The effect of water on the morphology of BaO/Al₂O ₃-based NO_x storage materials was investigated using Fourier transform infrared spectroscopy, temperature programmed desorption, and time-resolved synchrotron X-ray diffraction techniques. The results of this multispectroscopy study reveal that in the presence of water surface Ba-nitrates convert to bulk nitrates and water facilitates the formation of large Ba(NO₃)₂ particles. The conversion of surface to bulk Ba-nitrates is completely reversible (i.e., after the removal of water from the storage material a significant fraction of the bulk nitrates reconverts to surface nitrates). NO₂ exposure of a H₂O-containing (wet) BaO/Al₂O₃ sample results in the formation of nitrites and bulk nitrates exclusively (i.e., no surface nitrates form). After further exposure to NO₂, the nitrites completely convert to bulk nitrates. The amount of NO_x taken up by the storage material, however, is essentially unaffected by the presence of water regardless of whether the water was dosed prior to or after NO₂ exposure. On the basis of the results of this study, we are now able to explain most of the observations reported in the literature on the effect of water on NO_x uptake on similar storage materials.

Original language	English (US)
Pages (from-to)	4678-4687
Number of pages	10
Journal	Journal of Physical Chemistry C
Volume	111
Issue number	12
DOIs	https://doi.org/10.1021/jp067932v
State	Published - Mar 29 2007
Externally published	Yes

All Science Journal Classification (ASJC) codes

Electronic, Optical and Magnetic Materials
General Energy
Physical and Theoretical Chemistry
Surfaces, Coatings and Films

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10.1021/jp067932v

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title = "Water-induced morphology changes in BaO/γ-Al2O3 NOx storage materials: An FTIR, TPD, and time-resolved synchrotron XRD study",

abstract = "The effect of water on the morphology of BaO/Al2O 3-based NOx storage materials was investigated using Fourier transform infrared spectroscopy, temperature programmed desorption, and time-resolved synchrotron X-ray diffraction techniques. The results of this multispectroscopy study reveal that in the presence of water surface Ba-nitrates convert to bulk nitrates and water facilitates the formation of large Ba(NO3)2 particles. The conversion of surface to bulk Ba-nitrates is completely reversible (i.e., after the removal of water from the storage material a significant fraction of the bulk nitrates reconverts to surface nitrates). NO2 exposure of a H2O-containing (wet) BaO/Al2O3 sample results in the formation of nitrites and bulk nitrates exclusively (i.e., no surface nitrates form). After further exposure to NO2, the nitrites completely convert to bulk nitrates. The amount of NOx taken up by the storage material, however, is essentially unaffected by the presence of water regardless of whether the water was dosed prior to or after NO2 exposure. On the basis of the results of this study, we are now able to explain most of the observations reported in the literature on the effect of water on NOx uptake on similar storage materials.",

author = "J{\'a}nos Szanyi and Kwak, {Ja Hun} and Kim, {Do Heui} and Xianqin Wang and Ricardo Chimentao and Jonathan Hanson and Epling, {William S.} and Peden, {Charles H.F.}",

year = "2007",

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T2 - An FTIR, TPD, and time-resolved synchrotron XRD study

AU - Szanyi, János

AU - Kwak, Ja Hun

AU - Kim, Do Heui

AU - Wang, Xianqin

AU - Chimentao, Ricardo

AU - Hanson, Jonathan

AU - Epling, William S.

AU - Peden, Charles H.F.

PY - 2007/3/29

Y1 - 2007/3/29

N2 - The effect of water on the morphology of BaO/Al2O 3-based NOx storage materials was investigated using Fourier transform infrared spectroscopy, temperature programmed desorption, and time-resolved synchrotron X-ray diffraction techniques. The results of this multispectroscopy study reveal that in the presence of water surface Ba-nitrates convert to bulk nitrates and water facilitates the formation of large Ba(NO3)2 particles. The conversion of surface to bulk Ba-nitrates is completely reversible (i.e., after the removal of water from the storage material a significant fraction of the bulk nitrates reconverts to surface nitrates). NO2 exposure of a H2O-containing (wet) BaO/Al2O3 sample results in the formation of nitrites and bulk nitrates exclusively (i.e., no surface nitrates form). After further exposure to NO2, the nitrites completely convert to bulk nitrates. The amount of NOx taken up by the storage material, however, is essentially unaffected by the presence of water regardless of whether the water was dosed prior to or after NO2 exposure. On the basis of the results of this study, we are now able to explain most of the observations reported in the literature on the effect of water on NOx uptake on similar storage materials.

AB - The effect of water on the morphology of BaO/Al2O 3-based NOx storage materials was investigated using Fourier transform infrared spectroscopy, temperature programmed desorption, and time-resolved synchrotron X-ray diffraction techniques. The results of this multispectroscopy study reveal that in the presence of water surface Ba-nitrates convert to bulk nitrates and water facilitates the formation of large Ba(NO3)2 particles. The conversion of surface to bulk Ba-nitrates is completely reversible (i.e., after the removal of water from the storage material a significant fraction of the bulk nitrates reconverts to surface nitrates). NO2 exposure of a H2O-containing (wet) BaO/Al2O3 sample results in the formation of nitrites and bulk nitrates exclusively (i.e., no surface nitrates form). After further exposure to NO2, the nitrites completely convert to bulk nitrates. The amount of NOx taken up by the storage material, however, is essentially unaffected by the presence of water regardless of whether the water was dosed prior to or after NO2 exposure. On the basis of the results of this study, we are now able to explain most of the observations reported in the literature on the effect of water on NOx uptake on similar storage materials.

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Water-induced morphology changes in BaO/γ-Al₂O₃ NO_x storage materials: An FTIR, TPD, and time-resolved synchrotron XRD study

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