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

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• 作者：Christian Bonatto Minella ; Claudio Pistidda ; Sebastiano Garroni ; Pau Nolis ; Maria Dolors Bar贸 ; Oliver Gutfleisch ; Thomas Klassen ; R眉diger Bormann ; Martin Dornheim
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：February 28, 2013
• 年：2013
• 卷：117
• 期：8
• 页码：3846-3852
• 全文大小：390K
• 年卷期：v.117,no.8(February 28, 2013)
• ISSN：1932-7455

文摘

The Ca(BH₄)₂鈥揗gH₂ 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 掳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鈥搉uclear 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鈥揗gH₂ 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.