Superior low-temperature hydrogen release from the ball-milled NH3BH3-LiNH2-LiBH4 composite

In the present study, we employed a multi-component combination strategy to constitute an AB/LiNH2/LiBH4 composite system. Our study found that mechanically milling the AB/LiNH2/LiBH4 mixture in a 1:1:1 molar ratio resulted in the formation of LiNH2BH3 (LiAB) and new crystalline phase(s). A spectral study of the post-milled and the relevant samples suggests that the new phase(s) is likely ammoniate(s) with a formula of Li2-x(NH3)(NH2BH3)(1-x)(BH4) (0 < x < 1). The decomposition behaviors of the Li2-x(NH3)(NH2BH3)(1-x)(BH4)/xLiAB composite were examined using thermal analysis and volumetric method in a wide temperature range. It was found that the composite exhibited advantageous dehydrogenation properties over LiAB and LiAB center dot NH3 at moderate temperatures. For example, it can release similar to 7.1 wt% H-2 of purity at temperature as low as 60 degrees C, with both the dehydrogenation rate and extent far exceeding that of LiAB and LiAB center dot NH3. A selectively deuterated composite sample has been prepared and examined to gain insight into the dehydrogenation mechanism of the Li2-x(NH3)(NH2BH3)(1-x)(BH4)/xLiAB composite. It was found that the LiBH4 component does not participate in the dehydrogenation reaction at moderate temperatures, but plays a key role in strengthening the coordination of NH3. This is believed to be a major mechanistic reason for the favorable dehydrogenation property of the composite at moderate temperatures. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.