The synthesis, structure and dehydrogenation of calcium borohydride hydrazinates

Calcium borohydride hydrazinates, Ca(BH4)2-nN2H4 (n 1⁄4 4/3, 1, 2, 3) have been synthesized successfully. In particular, Ca(BH4)2 2N2H4 crystallizes in a monoclinic space group of C2/m with the lattice parameters of a 1⁄4 10.1385 Å, b 1⁄4 8.6342 Å, c 1⁄4 4.6384 Å, b 1⁄4 106.467 . It can release 5.9 equiv. gas/Ca(BH4)2 (approximately 8.8 wt. % H2) at 240 C. Ca(BH4)2-N2H4 and Ca(BH4)2-4/3N2H4, on the other hand, show superior dehydrogenation properties under the same condition, i.e., around 9.2 wt.% and 10.8 wt.% hydrogen can be released from these two samples, respectively. It is suggested that two dehydrogenation pathways, i.e., direct combination of H -Hdþ and ammonia-intermediated mechanisms, are likely to be involved in the process of dehydrogenation. Furthermore, the dehydrogenation temperature can be reduced significantly from 240 C to 140 C by introducing a Fe-based catalyst. Copyright © 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights