LiBH4•NH3BH3: A new lithium borohydride ammonia borane compound with a novel structure and favorable hydrogen storage properties

Mechanically milling milling ammonia borane and lithium borohydride in equivalent molar ratio results in the formation of a new complex, LiBH4 center dot NH3BH3. Its structure was successfully determined using combined X-ray diffraction and first-principles calculations. LiBH4 center dot NH3BH3 was carefully studied in terms of its decomposition behavior and reversible dehydrogenation property, particularly in comparison with the component phases. In parallel to the property examination, X-ray diffraction and Fourier transformation infrared spectroscopy techniques were employed to monitor the phase evolution and bonding structure changes in the reaction process. Our study found that LiBH4 center dot NH3BH3 first disproportionates into (LiBH4)(2)center dot NH3BH3 and NH3BH3, and the resulting mixture exhibits a three-step decomposition behavior upon heating to 450 degrees C, totally yielding similar to 15.7 wt% hydrogen. Interestingly, it was found that h-BN was formed at such a moderate temperature. And owing to the in situ formation of h-BN, LiBH4 center dot NH3BH3 exhibits significantly improved reversible dehydrogenation properties in comparison with the LiBH4 phase. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.