Journal of Alloys and Compounds 509 (2011) 751–757
Journal of Alloys and Compounds
journal homepage: www.elsevier.com/locate/jallcom
Destabilization of LiBH by (Ce, La)(Cl, F) for hydrogen storage
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Bang Jie Zhang , Bin Hong Liu , Zhou Peng Lib
a
a,∗
a
Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, PR China
Department of Chemical Engineering, Zhejiang University, Hangzhou 310027, PR China
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 19 July 2010
Received in revised form 6 September 2010
Accepted 8 September 2010
Available online 22 September 2010
The mixtures of LiBH4 with halides of Ce or La in a molar ratio of 3:1 were investigated to explore
their hydrogen storage properties. The ball milling of LiBH4 with chloride of Ce or La yielded Ce(BH4)3
and La(BH4)3, while fluoride of Ce or La did not react with LiBH4 during extended ball milling at room
◦
temperature. The dehydrogenation temperatures of the ball-milled mixtures were reduced to 220–320 C,
which were much lower than that of pure LiBH4. The diborane emission during hydrogen release was
observed at a low level. The dehydrogenation temperature is found to be affected by the composition of
rare earth halides, but less influenced by ball milling time. The endothermic dehydrogenation reactions
produced lithium halides, hydrides and borides of the corresponding rare earth element. Moreover, the
LiBH4 + 1/3(Ce, La)(Cl, F)3 showed partial reversibility through the formation of an unknown borohydride,
allowing for a potential hydrogen storage system.
Keywords:
Hydrogen storage material
Borohydride
Halides of rare earth
Dehydrogenation
Reversibility
© 2010 Elsevier B.V. All rights reserved.
1
. Introduction
Hydrogen is regarded as an ideal energy carrier due to its
of LiBH4 and MgH2 could effectively destabilize the system, result-
ing in reversible hydrogen storage at reduced temperatures. Other
additives like Al [9,10], carbon materials [11,12], TiO , V O5 [13,14]
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high energy density and environmental-friendly nature. However,
hydrogen has to be stored efficiently and safely in versatile appli-
cations. Currently, extensive effort is being devoted to exploring
new hydrogen storage materials with high gravimetric and vol-
umetric hydrogen densities [1–8]. Metal borohydrides are one
group of compounds with the highest hydrogen capacities and
and halides such as TiCl , TiF3 and ZnF2 [15] could also reduce the
dehydrogenation temperature of LiBH4.
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Among various additives, transition metal halides are one group
of destabilizing agents for LiBH . Halides of Ti [15] and Zr [17],
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chlorides of Mn [23], chlorides of Fe, Co, Ni [24], halides of Zn
[15,17] have been added to reduce the dehydrogenation temper-
thus considered as candidates for hydrogen storage. LiBH , as the
ature of LiBH . The main reason for the destabilization is due to
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representative, contains 18.4 wt.% hydrogen and is thus attract-
ing considerable attentions as a promising material for hydrogen
storage [3–4,6–24].
the instability of corresponding transition metal borohydrides [19].
n+
Nakamori et al. [16] suggested that the cation M in M(BH )n plays
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an important role in deciding the stability of borohydride. The ther-
The reversible hydrogen storage of LiBH4 could be achieved
through following reaction.
mal desorption temperature of M(BH )n is inversely proportional to
the Pauling electronegativity of the metal M. As the electronagativ-
ities of transition metals are larger than that of Li, the stabilities of
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LiBH = LiH + B + 3/2H2
(1)
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their borohydrides will be much lower than that of LiBH , enabling
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However, reversible hydrogen storage of LiBH4 requires harsh
conditions. For example, hydrogen desorption from LiBH4 takes
dehydrogenation at lower temperatures. However, the additions
of these transition metal halides often result in irreversibility of
the systems, which is undesirable for developing hydrogen storage
materials.
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place at temperature as high as 400 C, while the re-hydrogenation
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needs 600 C and 35 MPa [3]. Therefore, it is necessary to destabilize
LiBH and enable hydrogen desorption and absorption at mild con-
Recently, it was reported by Gennari et al. [22] that Ce(BH4)3
was synthesized through ball milling the mixture of LiBH4 and
CeCl3, and desorbed hydrogen at low temperatures. Moreover, they
found that the decomposed sample could absorb some hydrogen.
However, they did not report further the re-hydrogenation pro-
cess. This result inspires an expectation for a potentially reversible
hydrogen storage system. Therefore in this study, we investi-
gated the dehydrogenation and re-hydrogenation process of the
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ditions. Some additives were found to be effective in destabilizing
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hydrogen below 300 C. Vajo et al. [6,7] found that the combination
∗ Corresponding author. Tel.: +86 571 87951770; fax: +86 571 87951770.
0
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doi:10.1016/j.jallcom.2010.09.066