Reaction of NO2 with a pure, thick BaO film: the effect of temperature on the nature of NOx species formed
The adsorption and reaction of NO2 on a thick (>30 ML), pure BaO film deposited onto an Al2O3/NiAl(110) substrate were investigated in the temperature range of 300 – 660 K using temperature programmed desorption (TPD), infrared reflection absorption spectroscopy (IRAS), and x-ray photoelectron spectroscopy (XPS) techniques. The adsorption of NO2 on BaO at room temperature results in the formation of nitrite-nitrate ion pairs. During thermal desorption the nitrite species decompose first, releasing an NO molecule and leaving an O on the surface, while nitrate species decompose in two steps at higher temperatures: at lower temperature as NO2 only, then, at higher temperature, as NO + O2. In cyclic experiments when the BaO film was exposed to NO2 at 300 K, followed by annealing to 575 K, a large amount of NOx was stored as nitrates, and no saturation was achieved even after the 10th adsorption/anneal cycle. This suggests the gradual conversion of the BaO film into barium nitrate clusters at elevated temperatures. The rate of nitrate formation increases as the sample temperature during NO2 exposure increases up to 610 K, while at even higher temperatures the amount of nitrates formed decreases. NO2 adsorption on the thick BaO film at 610 K results in the formation of strongly bound nitrates as the major NOx species.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 950177
- Report Number(s):
- PNNL-SA-62106; 19198; KC0302010
- Journal Information:
- Journal of Physical Chemistry C, 113(6):2134-2140, Journal Name: Journal of Physical Chemistry C, 113(6):2134-2140 Journal Issue: 6 Vol. 113; ISSN 1932-7447
- Country of Publication:
- United States
- Language:
- English
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