A novel aided-cation strategy to advance the dehydrogenation of calcium borohydride monoammoniate

The crystal structure of a promising hydrogen storage material, calcium borohydride monoammoniate (Ca(BH4)(2)center dot NH3), is reported. Structural analysis revealed that this compound crystallizes in an orthorhombic structure (space group Pna2(1)) with unit-cell parameters of a = 8.4270 angstrom, b = 12.0103 angstrom, c = 5.6922 angstrom and V = 576.1121 angstrom(3), in which the Ca atom centrally resides in a slightly distorted octahedral environment furnished by five B atoms from BH4 units and one N atom from the NH3 unit. As Ca(BH4)(2)center dot NH3 tends to release ammonia rather than hydrogen when heated in argon, a novel aided-cation strategy via combining this compound with LiBH4 was employed to advance its dehydrogenation. It shows that the interaction of the two potential hydrogen storage substances upon heating, based on a promoted recombination reaction of BH and NH groups, enables a significant mutual dehydrogenation improvement beyond them alone, resulting in more than 12 wt% high-pure H-2 (>99%) released below 250 degrees C. The synergetic effect of associating the dihydrogen reaction with mutually aided-metal cations on optimizing the dehydrogenation of this kind of composites may serve as an alternative strategy for developing and expanding the future B-N-H systems with superior and tuneable dehydrogenation properties.