Ammine Magnesium Borohydride Complex as a New Material for Hydrogen Storage: Structure and Properties of Mg(BH4)2 . 2NH3
The ammonia complex of magnesium borohydride Mg(BH4)2{center_dot}2NH3 (I), which contains 16.0 wt % hydrogen, is a potentially promising material for hydrogen storage. This complex was synthesized by thermal decomposition of a hexaaammine complex Mg(BH4)2{center_dot}6NH3 (II), which crystallizes in the cubic space group Fmm with unit cell parameter a = 10.82(1) Angstroms and is isostructural to Mg(NH3)6Cl2. We solved the structure of I that crystallizes in the orthorhombic space group Pcab with unit cell parameters a = 17.4872(4) Angstroms, b = 9.4132(2) Angstroms, c = 8.7304(2) Angstroms, and Z = 8. This structure is built from individual pseudotetrahedral molecules Mg(BH4)2{center_dot}2NH3 containing one bidentate BH4 group and one tridentate BH4 group that pack into a layered crystal structure mediated by NH{center_dot}{center_dot}{center_dot}HB dihydrogen bonds. Complex I decomposes endothermically starting at 150 C, with a maximum hydrogen release rate at 205 C, which makes it competitive with ammonia borane BH3NH3 as a hydrogen storage material.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 959860
- Report Number(s):
- BNL-82846-2009-JA; INOCAJ; TRN: US201016%%1004
- Journal Information:
- Inorganic Chemistry, Vol. 47; ISSN 0020-1669
- Country of Publication:
- United States
- Language:
- English
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