Thermodynamic Properties and Reversible Hydrogenation of LiBH4-Mg2FeH6 Composite Materials
Thermodynamic Properties and Reversible Hydrogenation of LiBH4-Mg2FeH6 Composite Materials
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DOI：
10.3390/inorganics5040081
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发表时间：
2017-12-01
期刊：
影响因子：
2.9
通讯作者：
Orimo, Shin-ichi
中科院分区：
文献类型：
--
作者：
Li, Guanqiao;Matsuo, Motoaki;Orimo, Shin-ichi
在以前的研究中，复合物LiBH_4和Mg_2Fe_H_6在球磨复合材料（1 - x）LiBH_4 + xMg（2）Fe_H（6）时同时发生脱氢。同时释放的氢导致的脱氢温度降低多达150 K时相比，LiBH 4。这也导致Mg 2FeH 6的改性脱氢性能。化学计量比的LiBH 4和Mg 2FeH 6之间的同时脱氢行为尚未被理解。因此，在目前的工作中，我们使用的摩尔比x = 0.25，0.5，和0.75，并研究了等温脱氢过程通过压力组成等温（PCT）测量。结果表明，所有复合材料都发生了相同的化学计量反应，反应中LiBH 4与Mg 2FeH 6的摩尔比x = 0.5。由于最佳的组成比，复合材料表现出增强的再氢化和可逆性能：x = 0.5复合材料完全再氢化的温度和压力分别为673 K和20 MPa H2，远低于LiBH 4部分再氢化所需的温度和压力。此外，x = 0.5的复合材料可以可逆氢化超过四个循环，而不会降低其H-2容量。
In previous studies, complex hydrides LiBH4 and Mg2FeH6 have been reported to undergo simultaneous dehydrogenation when ball-milled as composite materials (1 - x)LiBH4 + xMg(2)FeH(6). The simultaneous hydrogen release led to a decrease of the dehydrogenation temperature by as much as 150 K when compared to that of LiBH4. It also led to the modified dehydrogenation properties of Mg2FeH6. The simultaneous dehydrogenation behavior between stoichiometric ratios of LiBH4 and Mg2FeH6 is not yet understood. Therefore, in the present work, we used the molar ratio x = 0.25, 0.5, and 0.75, and studied the isothermal dehydrogenation processes via pressure-composition-isothermal (PCT) measurements. The results indicated that the same stoichiometric reaction occurred in all of these composite materials, and x = 0.5 was the molar ratio between LiBH4 and Mg2FeH6 in the reaction. Due to the optimal composition ratio, the composite material exhibited enhanced rehydrogenation and reversibility properties: the temperature and pressure of 673 K and 20 MPa of H-2, respectively, for the full rehydrogenation of x = 0.5 composite, were much lower than those required for the partial rehydrogenation of LiBH4. Moreover, the x = 0.5 composite could be reversibly hydrogenated for more than four cycles without degradation of its H-2 capacity.