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Pressure Effect on the 2NaH+MgB2 Hydrogen Absorption Reaction

Pistidda, Claudio; Garroni, Sebastiano; Minella, Christian Bonatto; Dolci, Francesco; Jensen, Torben R.; Nolis, Pau; Boesenberg, Ulrike; Cerenius, Yngve LU ; Lohstroh, Wiebke and Fichtner, Maximilian, et al. (2010) In Journal of Physical Chemistry C 114(49). p.21816-21823
Abstract
The hydrogen absorption mechanism of the 2NaH + MgB2 system has been investigated in detail. Depending on the applied hydrogen pressure, different intermediate phases are observed. In the case of absorption measurements performed under 50 bar of hydrogen pressure, NaBH4 is found not to be formed directly. Instead, first an unknown phase is formed, followed upon further heating by the formation of NaMgH3 and a NaH-NaBH4 molten salt mixture; only at the end after heating to 380 degrees C do the reflections of the crystalline NaBH4 appear. In contrast, measurements performed at lower hydrogen pressure (5 bar of H-2), but under the same temperature conditions, demonstrate that the synthesis of NaBH4 is possible without occurrence of the... (More)
The hydrogen absorption mechanism of the 2NaH + MgB2 system has been investigated in detail. Depending on the applied hydrogen pressure, different intermediate phases are observed. In the case of absorption measurements performed under 50 bar of hydrogen pressure, NaBH4 is found not to be formed directly. Instead, first an unknown phase is formed, followed upon further heating by the formation of NaMgH3 and a NaH-NaBH4 molten salt mixture; only at the end after heating to 380 degrees C do the reflections of the crystalline NaBH4 appear. In contrast, measurements performed at lower hydrogen pressure (5 bar of H-2), but under the same temperature conditions, demonstrate that the synthesis of NaBH4 is possible without occurrence of the unknown phase and of NaMgH3. This indicates that the reaction path can be tuned by the applied hydrogen pressure. The formation of a NaH-NaBH4 molten salt mixture is observed also for the measurement performed under 5 bar of hydrogen pressure with the formation of free Mg. However, under this pressure condition the formation of crystalline NaBH4 is observed only during cooling at 367 degrees C. For none of the applied experimental conditions has it been possible to achieve the theoretical gravimetric hydrogen capacity of 7.8 wt %. (Less)
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publication status
published
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Journal of Physical Chemistry C
volume
114
issue
49
pages
21816 - 21823
publisher
The American Chemical Society
external identifiers
  • wos:000284990800125
  • scopus:78650264960
ISSN
1932-7447
DOI
10.1021/jp107363q
language
English
LU publication?
yes
id
36202b6c-d915-4a80-ba1f-1053212e5165 (old id 1751688)
date added to LUP
2010-12-29 13:57:41
date last changed
2018-05-29 10:58:12
@article{36202b6c-d915-4a80-ba1f-1053212e5165,
  abstract     = {The hydrogen absorption mechanism of the 2NaH + MgB2 system has been investigated in detail. Depending on the applied hydrogen pressure, different intermediate phases are observed. In the case of absorption measurements performed under 50 bar of hydrogen pressure, NaBH4 is found not to be formed directly. Instead, first an unknown phase is formed, followed upon further heating by the formation of NaMgH3 and a NaH-NaBH4 molten salt mixture; only at the end after heating to 380 degrees C do the reflections of the crystalline NaBH4 appear. In contrast, measurements performed at lower hydrogen pressure (5 bar of H-2), but under the same temperature conditions, demonstrate that the synthesis of NaBH4 is possible without occurrence of the unknown phase and of NaMgH3. This indicates that the reaction path can be tuned by the applied hydrogen pressure. The formation of a NaH-NaBH4 molten salt mixture is observed also for the measurement performed under 5 bar of hydrogen pressure with the formation of free Mg. However, under this pressure condition the formation of crystalline NaBH4 is observed only during cooling at 367 degrees C. For none of the applied experimental conditions has it been possible to achieve the theoretical gravimetric hydrogen capacity of 7.8 wt %.},
  author       = {Pistidda, Claudio and Garroni, Sebastiano and Minella, Christian Bonatto and Dolci, Francesco and Jensen, Torben R. and Nolis, Pau and Boesenberg, Ulrike and Cerenius, Yngve and Lohstroh, Wiebke and Fichtner, Maximilian and Dolores Baro, Maria and Bormann, Ruediger and Dornheim, Martin},
  issn         = {1932-7447},
  language     = {eng},
  number       = {49},
  pages        = {21816--21823},
  publisher    = {The American Chemical Society},
  series       = {Journal of Physical Chemistry C},
  title        = {Pressure Effect on the 2NaH+MgB2 Hydrogen Absorption Reaction},
  url          = {http://dx.doi.org/10.1021/jp107363q},
  volume       = {114},
  year         = {2010},
}