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Tailoring the Properties of Ammine Metal Borohydrides for Solid‐State Hydrogen Storage
Author(s) -
Jepsen Lars H.,
Ley Morten B.,
Filinchuk Yaroslav,
Besenbacher Flemming,
Jensen Torben R.
Publication year - 2015
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.201500029
Subject(s) - borohydride , chemistry , electronegativity , metal , bimetallic strip , hydrogen storage , manganese , inorganic chemistry , crystal structure , ammonia , crystallography , solid solution , hydrogen , metal halides , halide , thermal decomposition , x ray crystallography , diffraction , catalysis , organic chemistry , physics , optics
A series of halide‐free ammine manganese borohydrides, Mn(BH 4 ) 2 ⋅ n NH 3 , n =1, 2, 3, and 6, a new bimetallic compound Li 2 Mn(BH 4 ) 4 ⋅6NH 3 , and the first ammine metal borohydride solid solution Mg 1− x Mn x (BH 4 ) 2 ⋅6NH 3 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(BH 4 ) 2 and NH 3 provides Mn(BH 4 ) 2 ⋅6NH 3 . The number of NH 3 per Mn has been varied by mechanochemical treatment of Mn(BH 4 ) 2 ⋅6NH 3 ‐Mn(BH 4 ) 2 mixtures giving rise to increased hydrogen purity for n / m ≤1 for M(BH 4 ) m ⋅ n NH 3 . The structures of Mg(BH 4 ) 2 ⋅3NH 3 and Li 2 Mg(BH 4 ) 4 ⋅6NH 3 have been revisited and new structural models are presented. Finally, we demonstrate that ammonia destabilizes metal borohydrides with low electronegativity of the metal ( χ p <∼1.6), while metal borohydrides with high electronegativity ( χ p >∼1.6) are generally stabilized.