A Novel Li鈥揅a鈥揃鈥揌 Complex Borohydride: Its Synthesis and Hydrogen Storage Properties

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• 作者：Kun Jiang ; Xuezhang Xiao ; Shuaishuai Deng ; Miao Zhang ; Shouquan Li ; Hongwei Ge ; Lixin Chen
• 刊名：Journal of Physical Chemistry C
• 出版年：2011
• 出版时间：October 13, 2011
• 年：2011
• 卷：115
• 期：40
• 页码：19986-19993
• 全文大小：1088K
• 年卷期：v.115,no.40(October 13, 2011)
• ISSN：1932-7455

文摘

The synthesis and hydrogen-storage properties of the mixed alkali metal and alkaline-earth metal borohydride are systematically investigated. It is found that mechanical milling a mixture of LiBH₄ and CaCl₂ with molar ratio of 3:1 in tetrahydrofuran (THF) forms a new LiBH₄路Ca(BH₄)₂路2THF compound. Thermal analysis indicates that the decomposition process of the new compound involves four steps: (1) LiBH₄路Ca(BH₄)₂路2THF decomposes first into high temperature phase of LiBH₄, CaB₆, and an intermediate phase Ca鈥揃鈥揌鈥揅l hydride and synchronously releases a large number of H₂ and THF gas together with less B₂H₆; (2) the eutectic melting of LiBH₄ and Ca鈥揃鈥揌鈥揅l hydride; (3) Ca鈥揃鈥揌鈥揅l hydride decomposes into CaHCl, CaB₆, and a little H₂; (4) LiBH₄ reacts with CaHCl, generating H₂, CaH₂, CaB₆, LiH, and LiCl. The first dehydrogenation step starts at ca. 70 掳C, which is much lower than that of the pristine LiBH₄ and Ca(BH₄)₂. According to Kissenger鈥檚 equation, the activation energies of the different dehydrogenation steps are respectively 291.95, 132.06, and 117.13 kJ/mol, except the second decomposition step. Moreover, this new compound LiBH₄路Ca(BH₄)₂路2THF is proved to be partially reversible, which can release 5.63 wt % hydrogen in the second rehydrogenation/dehydrogenation cycle.