Hydrogen storage properties of Mg[BH4]2

T. Matsunaga, F. Buchter, P. Mauron, M. Bielman, Y. Nakamori, S. Orimo, N. Ohba, K. Miwa, S. Towata, A. Züttel

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Among the large variety of possible complex hydrides only few exhibit a large gravimetric hydrogen density and stability around 40 kJ mol-1H2. Mg[BH4]2 is based on theoretical approaches a complex hydride with an equilibrium hydrogen pressure of approximately 1 bar at room temperature and a hydrogen content of 14.9 mass%. The reaction of Li[BH4] with MgCl2 at elevated temperatures was investigated as a possible route to synthesize Mg[BH4]2. Li[BH4] reacts with MgCl2 at a temperature >523 K at a pressure of 10 MPa of hydrogen, where the product contains LiCl and Mg[BH4]2. The desorption pc-isotherm of the product obtained at 623 K shows two flat plateaus, which indicates that the decomposition of the product consists of a two-step reaction. The products of the first and the second decomposition reaction were analyzed by means of X-ray diffraction and found to be MgH2 and Mg, respectively. The enthalpy for the first decomposition reaction was determined to be ΔH = -39.3 kJ mol-1H2 by the Van't Hoff plot of the equilibrium measurements between 563 K and 623 K, which is significantly lower than that for pure Li[BH4] (ΔH = -74.9 kJ mol-1H2). However, only the second reaction step (MgH2 → Mg) is reversible at the condition up to 623 K at 10 MPa of hydrogen.

Original languageEnglish
Pages (from-to)583-588
Number of pages6
JournalJournal of Alloys and Compounds
Issue number1-2
Publication statusPublished - 2008 Jul 14


  • Hydrogen absorbing materials
  • Thermal analysis
  • Thermodynamic properties


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