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| Titel |
Identification of a BrOOO− intermediate species in the ozonolysis of bromide at the liquid/vapor interface from liquid jet XPS |
| VerfasserIn |
Shuzhen Chen, Luca Artiglia, Fabrizio Orlando, Pablo Corral-Arroyo, Jacinta Edebeli, Markus Ammann |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250139488
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| Publikation (Nr.) |
 EGU/EGU2017-2739.pdf |
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| Zusammenfassung |
| Oxidation of bromide by gas phase ozone (O3) in the absence of photochemistry is believed
to be one of the important dark reactions to produce HOBr as the starting point of the
multiphase cycling reaction mechanisms that release bromide out of sea water, sea spray or
marine aerosols from aqueous solution that later drive O3 depleting chemistry in the
troposphere [1]. The reaction of bromide with O3 occurs through an acid catalyzed
mechanism involving a BrOOO− complex as an intermediate [2]. Slow oxidation of bromide
by O3 in the bulk aqueous phase is of limited relevance; previous kinetic experiments have
suspected the reaction to be enhanced at the surface of aqueous solutions. Thus, identifying
BrOOO− at the interface would be a major step to understanding the multiphase oxidation of
bromide with O3.
Here, we provide a direct experimental evidence for the formation of a BrOOO− reaction
intermediate at the surface by investigating the reaction of aqueous solutions NaBr with gas
phase O3 after millisecond time scale exposure using the surface sensitive in situ liquid jet
X-ray photoelectron spectroscopy (XPS) at the Swiss Light Source (SLS). We acquired Br 3d
core level spectra of 0.125 M NaBr solution in presence and absence of ozone in the
gas phase. We found a new feature with a peak position shifted towards higher
binding energy (by ∼0.7 eV) compared to Br−, which was clearly different from the
Br 3d core levels spectra of hypobromite and bromate measured with reference
solutions. Our results suggest the appearance of the formation of the BrOOO− reaction
intermediate as a new component, in agreement with theoretical calculations of the Br−
ozonolysis mechanism [3]. Additionally, by varying the photoelectron kinetic energy
and thus probe depth via variation of the probing photon energy, the new feature
appears to be present near the liquid/vapor interface. Besides, kinetic experiments
for the reaction of O3 with bromide are ongoing to investigate the dependence on
the temperature, ozone concentration, which may give further information such
as the relative oxidation rate at the liquid/vapor interface versus that in the bulk
phase.
[1] S. Wang, et al., Proceedings of the National Academy of Sciences, 2015, 112,
9281-9286.
[2] Q. Liu, et al., Inorganic Chemistry, 2001, 40, 4436-4442.
[3] I. Gladich, et al., The Journal of Physical Chemistry A, 2015, 119, 4482-4488. |
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