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1
Pressure and temperature dependence of the decomposition pathway of LiBH4

Yan, Yigang,Remhof, Arndt,Hwang, Son-Jong,Li, Hai-Wen,Mauron, Philippe,Orimo, Shin-ichi,Zü,ttel, Andreas The Royal Society of Chemistry 2012 Physical chemistry chemical physics Vol.14 No.18
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The decomposition pathway is crucial for the applicability of LiBH4 as a hydrogen storage material. We discuss and compare the different decomposition pathways of LiBH4 according to the thermodynamic parameters and show the experimental ways to realize them. Two pathways, i.e. the direct decomposition into boron and the decomposition via Li2B12H12, were realized under appropriate conditions, respectively. By applying a H2 pressure of 50 bar at 873 K or 10 bar at 700 K, LiBH4 is forced to decompose into Li2B12H12. In a lower pressure range of 0.1 to 10 bar at 873 K and 800 K, the concurrence of both decomposition pathways is observed. Raman spectroscopy and 11B MAS NMR measurements confirm the formation of an intermediate Li2B12H12 phase (mostly Li2B12H12 adducts, such as dimers or trimers) and amorphous boron. Graphic AbstractThe thermodynamic properties of LiBH4 and its possible decomposition products and intermediates allow flexibility in selection of the decomposition pathway by tuning the external parameters such as pressure and temperature. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2cp40131b'>
2
Thermal properties of Y(BH4)3 synthesized via two different methods

Park, K.,Lee, H.S.,Remhof, A.,Lee, Y.S.,Yan, Y.,Kim, M.Y.,Kim, S.J.,Zuttel, A.,Cho, Y.W. Pergamon Press ; Elsevier Science Ltd 2013 INTERNATIONAL JOURNAL OF HYDROGEN ENERGY - Vol.38 No.22
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Y(BH4)3 is one of the candidates for solid-state hydrogen storage, which contains 9.06 wt% of hydrogen. In this study, the thermal properties of Y(BH4)3 synthesized via two different methods are extensively examined. One method relies on the solid-solid metathesis reaction between LiBH4 and YCl3, and the other method is the gas-solid reaction between B2H6 and YH3. The two samples are studied by differential scanning calorimetry, thermogravimetry, and X-ray diffraction. They exhibit distinctly different polymorphic phase transformation and melting. It turns out that the side product LiCl in the metathesis reaction, which has been regarded as being inert, shifts the melting point and promotes the formation of YB4 during decomposition. Differential scanning calorimetry and in situ X-ray diffraction data indicate that the addition of LiBH4 to Y(BH4)3 induces co-melting as is found in the cases of LiBH4-Ca(BH4)2 or LiBH4-Mg(BH4)2. Melt infiltration of Y(BH4)3 into mesoporous carbon cage confirms such melting behavior.
3
The effect of Al on the hydrogen sorption mechanism of LiBH4

Friedrichs, O.,Kim, J. W.,Remhof, A.,Buchter, F.,Borgschulte, A.,Wallacher, D.,Cho, Y. W.,Fichtner, M.,Oh, K. H.,Zü,ttel, A. Royal Society of Chemistry 2009 Physical chemistry chemical physics Vol.11 No.10
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We demonstrate the synthesis of LiBH4 from LiH and AlB2 without the use of additional additives or catalysts at 450 °C under hydrogen pressure of 13 bar to the following equation: 2LiH + AlB2 + 3H2↔ 2LiBH4 + Al. By applying AlB2 the kinetics of the formation of LiBH4 is strongly enhanced compared to the formation from elemental boron. The formation of LiBH4 during absorption requires the dissociation of AlB2, i.e. a coupled reaction. The observed low absorption-pressure of 13 bar, measured during hydrogen cycling, is explained by a low stability of AlB2, in good agreement with theoretical values. Thus starting from AlB2 instead of B has a rather low impact on the thermodynamics, and the effect of AlB2 on the formation of LiBH4 is of kinetic nature facilitating the absorption by overcoming the chemical inertness of B. For desorption, the decomposition of LiBH4 is not indispensably coupled to the immediate formation of AlB2. LiBH4 may decompose first into LiH and elemental B and during a slower second step AlB2 is formed. In this case, no destabilization will be observed for desorption. However, due to similar stabilities of LiBH4 and LiBH4/Al a definite answer on the desorption mechanism cannot be given and neither a coupled nor decoupled desorption can be excluded. At low hydrogen pressures the reaction of LiH and Al gives LiAl under release of hydrogen. The formation of LiAl increases the total hydrogen storage capacity, since it also contributes to the LiBH4 formation in the absorption process. Graphic AbstractLiBH4 (LiBD4) is synthesized by hydrogenation of LiH (LiD) and AlB2 without use of additional additives or catalysts. The reversible reaction mechanism is investigated. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b814282c'>

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