Improved Dehydrogenation Properties of Ca(BH4)2•nNH3 (n=1, 2, and 4) Combined with Mg(BH4)2

As Ca(BH4)(2)center dot nNH(3) (n = 1, 2, and 4) tends to release ammonia rather than hydrogen when heated in argon, an aided-cation strategy via combining these compounds with Mg(BH4)(2) is employed to advance their dehydrogenation. It shows that the interaction between the two hydrogen storage systems, based on a promoted recombination reaction of BH and NH groups, enables a significant mutual dehydrogenation improvement beyond them alone. Dehydrogenation results show that the Ca(BH4)(2)center dot 4NH(3)/Mg(BH4)(2) composite starts to release hydrogen at around 62 degrees C and presents a hydrogen desorption capacity of > 9 wt % below 300 degrees C with a H-purity of 92.3 wt %. Furthermore, in the cases of Ca(BH4)(2)center dot 4NH(3)/2Mg(BH4)(2), Ca(BH4)(2)center dot 2NH(3)/Mg(BH4)(2), and Ca(BH4)(2)center dot NH3/Mg(BH4)(2), fairly pure hydrogen (> 99 wt %) is released upon heating from RT to 500 degrees C. Further investigation via introduction of isotope deuterium in the combined system reveals that the dehydrogenation reactions are mainly mediated by the combination of H delta+center dot center dot center dot H delta+ interactions, whereas H delta-center dot center dot center dot H delta- interactions also contribute in a complementary way.