Water-Induced Morphology Changes in BaO/gamma-Al2O3 NOx Storage Materials: an FTIR, TPD, and Time-Resolved Synchrotron XRD Study
The effect of water on the morphology of BaO/Al{sub 2}O{sub 3}-based NO{sub 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(NO{sub 3}){sub 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). NO{sub 2} exposure of a H{sub 2}O-containing (wet) BaO/Al{sub 2}O{sub 3} sample results in the formation of nitrites and bulk nitrates exclusively (i.e., no surface nitrates form). After further exposure to NO{sub 2}, the nitrites completely convert to bulk nitrates. The amount of NO{sub 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 NO{sub 2} 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{sub x} uptake on similar storage materials.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 930377
- Report Number(s):
- BNL-81099-2008-JA; TRN: US0901377
- Journal Information:
- Journal of Physical Chemistry C, Vol. 111; ISSN 1932-7447
- Country of Publication:
- United States
- Language:
- English
Similar Records
The interaction of NO2 with BaO: from cooperative adsorption to Ba(NO3)2 formation
BaO/Al2O3/NiAl(110) Model NOx Storage Materials. The effect of BaO film thickness on the amorphous-to-crystalline Ba(NO3)2 phase transition