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Tailoring the Properties of Ammine Metal Borohydrides for Solid-State Hydrogen Storage

DOI: 10.1002/cssc.201500029 DOI Help

Authors: Lars H. Jepsen (Interdisciplinary Nanoscience Center) , Morten B. Ley (Interdisciplinary Nanoscience Center) , Yaroslav Filinchuk (Institute of Condensed Matter and Nanosciences, Université catholique de Louvain) , Flemming Besenbacher (Interdisciplinary Nanoscience Center) , Torben R. Jensen (Interdisciplinary Nanoscience Center)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Chemsuschem , VOL 8 (8) , PAGES 1452 - 1463

State: Published (Approved)
Published: April 2015
Diamond Proposal Number(s): 9031

Abstract: A series of halide-free ammine manganese borohydrides, Mn(BH4)2⋅nNH3, n=1, 2, 3, and 6, a new bimetallic compound Li2Mn(BH4)4⋅6NH3, and the first ammine metal borohydride solid solution Mg1−xMnx(BH4)2⋅6NH3 are presented. Four new crystal structures have been determined by synchrotron radiation powder X-ray diffraction and the thermal decomposition is systematically investigated for all the new compounds. The solid-gas reaction between Mn(BH4)2 and NH3 provides Mn(BH4)2⋅6NH3. The number of NH3 per Mn has been varied by mechanochemical treatment of Mn(BH4)2⋅6NH3-Mn(BH4)2 mixtures giving rise to increased hydrogen purity for n/m≤1 for M(BH4)m⋅nNH3. The structures of Mg(BH4)2⋅3NH3 and Li2Mg(BH4)4⋅6NH3 have been revisited and new structural models are presented. Finally, we demonstrate that ammonia destabilizes metal borohydrides with low electronegativity of the metal (χp<∼1.6), while metal borohydrides with high electronegativity (χp>∼1.6) are generally stabilized.

Journal Keywords: Hydrogen Storage;Hydrides;Synchrotron Radiation;X-Ray Diffraction;Mechanochemistry

Subject Areas: Chemistry, Materials

Instruments: I11-High Resolution Powder Diffraction