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Title: A new family of metal borohydride guanidinate complexes: Synthesis, structures and hydrogen-storage properties

Journal Article · · Journal of Solid State Chemistry
 [1];  [2];  [2];  [1];  [1];  [1];  [3]
  1. National Institutes of Standards and Technology (NIST), Gaithersburg, MD (United States)
  2. University of Maryland, College Park, MD (United States)
  3. National Institutes of Standards and Technology (NIST), Gaithersburg, MD (United States); University of Maryland, College Park, MD (United States)
+ Show Author Affiliations

Here we report on a new class of complex hydrides: borohydride guanidinate complexes (MBH4·nCN3H5, M=Li, Mg, and Ca). They can be prepared via facile solid-state synthesis routes. Their crystal structures were successfully determined using a combination of X-ray diffraction, first-principles calculations and neutron vibrational spectroscopy. Among these compounds, Mg(BH4)2·6CN3H5 is composed of large complex Mg[CN3H5]62+ cations and surrounding BH4- ions, while Ca(BH4)2·2CN3H5 possesses layers of corner-sharing Ca[BH4]4(CN3H5)2 octahedra. Our dehydrogenation results show that ≈10 wt% hydrogen can be released from MBH4·nCN3H5 (M=Li, Mg, and Ca) at moderate temperatures with minimal ammonia and diborane contamination thanks to the synergistic effect of C-N bonds from guanidine and hydridic H from borohydrides leading to a weakening of the N-H bonds, thus impeding ammonia gas liberation. Further tuning the dehydrogenation with different cation species indicates that Mg(BH4)2·nCN3H5 can exhibit the optimum properties with nearly thermally neutral dehydrogenation and very high purity hydrogen release.

Research Organization:
National Institutes of Standards and Technology (NIST), Gaithersburg, MD (United States); Univ. of Maryland, College Park, MD (United States)
Sponsoring Organization:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Grant/Contract Number:
EE0002978
OSTI ID:
1534063
Alternate ID(s):
OSTI ID: 1459746
Journal Information:
Journal of Solid State Chemistry, Vol. 242, Issue P1; ISSN 0022-4596
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 10 works
Citation information provided by
Web of Science

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
borohydrides
guanidine
crystal structure determination
neutron vibrational spectroscopy
dehydrogenation
thermodynamics