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Ca(BH4)2+ MgH2: Desorption Reaction and Role of Mg on Its Reversibility

Minella, Christian Bonatto and Pistidda, Claudio and Garroni, Sebastiano and Nolis, Pau and Baró, Maria Dolors and Gutfleisch, Oliver and Klassen, Thomas and Bormann, Rüdiger and Dornheim, Martin (2013):
Ca(BH4)2+ MgH2: Desorption Reaction and Role of Mg on Its Reversibility.
In: The Journal of Physical Chemistry C, American Chemical Society Publications, pp. 3846-3852, 117, (8), ISSN 1932-7447, [Online-Edition: http://dx.doi.org/10.1021/jp312271s],
[Article]

Abstract

The Ca(BH4)2–MgH2 composite system represents a promising candidate for mobile hydrogen storage due to a 10.5 wt % theoretical hydrogen storage capacity and an estimated equilibrium temperature lower than 160 °C. For this system, the reversibility was achieved without further addition of additives. In this study, the decomposition path of the Ca(BH4)2 + MgH2 composite system is investigated in detail by in situ synchrotron radiation powder X-ray diffraction and differential scanning calorimetry combined with thermogravimetry. The sorption properties are analyzed by volumetric measurements. 11B{1H} solid state magic angle spinning–nuclear magnetic resonance was employed for the characterization of the final amorphous or nanocrystalline boron-based decomposition products. This study shows that the intermediate formation of Ca4Mg3H14 upon dehydrogenation of the Ca(BH4)2–MgH2 composite system is not a necessary step, and its presence can be adjusted modifying the preparation procedure. Moreover, the d-value mismatch calculated for the {111}CaB6/{1011}Mg plane pair is the lowest among the other plane pairs considered in the system. The mismatch in the third direction between CaB6 and Mg is also extremely good. These findings propose Mg as a supporter of the heterogeneous nucleation of CaB6 during decomposition of the Ca(BH4)2 + MgH2 composite system.

Item Type: Article
Erschienen: 2013
Creators: Minella, Christian Bonatto and Pistidda, Claudio and Garroni, Sebastiano and Nolis, Pau and Baró, Maria Dolors and Gutfleisch, Oliver and Klassen, Thomas and Bormann, Rüdiger and Dornheim, Martin
Title: Ca(BH4)2+ MgH2: Desorption Reaction and Role of Mg on Its Reversibility
Language: English
Abstract:

The Ca(BH4)2–MgH2 composite system represents a promising candidate for mobile hydrogen storage due to a 10.5 wt % theoretical hydrogen storage capacity and an estimated equilibrium temperature lower than 160 °C. For this system, the reversibility was achieved without further addition of additives. In this study, the decomposition path of the Ca(BH4)2 + MgH2 composite system is investigated in detail by in situ synchrotron radiation powder X-ray diffraction and differential scanning calorimetry combined with thermogravimetry. The sorption properties are analyzed by volumetric measurements. 11B{1H} solid state magic angle spinning–nuclear magnetic resonance was employed for the characterization of the final amorphous or nanocrystalline boron-based decomposition products. This study shows that the intermediate formation of Ca4Mg3H14 upon dehydrogenation of the Ca(BH4)2–MgH2 composite system is not a necessary step, and its presence can be adjusted modifying the preparation procedure. Moreover, the d-value mismatch calculated for the {111}CaB6/{1011}Mg plane pair is the lowest among the other plane pairs considered in the system. The mismatch in the third direction between CaB6 and Mg is also extremely good. These findings propose Mg as a supporter of the heterogeneous nucleation of CaB6 during decomposition of the Ca(BH4)2 + MgH2 composite system.

Journal or Publication Title: The Journal of Physical Chemistry C
Volume: 117
Number: 8
Publisher: American Chemical Society Publications
Divisions: 11 Department of Materials and Earth Sciences > Material Science > Functional Materials
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences
Date Deposited: 06 Jun 2013 08:12
Official URL: http://dx.doi.org/10.1021/jp312271s
Identification Number: doi:10.1021/jp312271s
Funders: The authors are grateful to the Marie-Curie European Research Training Network (Contract MRTN-CT-2006-03 5366/ COSY) for the financial suppor, M.D.B. acknowledges the partial financial support from the 2009-SGR-1292 project and from an ICREA- Academia award.
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