Unexpected kinetic effect of MgB2 in reactive hydride composites containing complex borohydrides
Unexpected kinetic effect of MgB2 in reactive hydride composites containing complex borohydrides
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DOI：
10.1016/j.jallcom.2006.09.048
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发表时间：
2007-08-16
影响因子：
6.2
通讯作者：
Bormann, Ruediger
中科院分区：
文献类型：
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作者：
Barkhordarian, Gagik;Klassen, Thomas;Bormann, Ruediger
轻金属复合硼氢化物由于具有高的储氢容量，是一种很有前途的储氢材料。然而，它们表现出两个主要缺点：它们的高热力学稳定性和它们的慢动力学。在本工作中，各种反应物对复杂硼氢化物的形成动力学的影响进行了研究。结果表明，以MgB 2代替B作为原料，LiBH 4、NaBH 4和Ca（BH 4）（2）生成的动力学势垒大大降低。由于在迄今为止研究的所有硼氢化物中都观察到这种动力学增强，因此所观察到的效果归因于B在Mg B中形成[BH 4]（-）络合物的更高反应性。此外，通过使用MgB 2代替元素B，相应的反应物减少了约10 W/mol H，同时大部分保留了高重量氢容量，即LiBH 4 + MgH 2为11.4重量%，Ca（BH 4）（2）+MgH 2为8.3重量%，NaBH 4 + MgH 2为7.8重量%。(c)2006 Elsevier B. V.保留所有权利。
Complex borohydrides of light metals are promising hydrogen storage materials due to their high hydrogen capacity. However, they exhibit two main drawbacks: their high thermodynamic stability and their slow kinetics. In the present work, the effect of various reactants on the formation kinetics of complex borohydrides is investigated. It is found that the kinetic barriers for the formation of LiBH4, NaBH4 and Ca(BH4)(2) are drastically reduced when MgB2 is used instead of B as starting material. Since this kinetic enhancement is observed in all borohydride studied so far, the observed effect is attributed to the higher reactivity of B in MgB, to form [BH4](-) complexes. In addition, by using MgB2 instead of elemental B, the corresponding reaction enthalpies are reduced by about 10 W/mol H, while the high gravimetric hydrogen capacities are largely preserved, i.e. LiBH4 + MgH2 with 11.4 wt%, Ca(BH4)(2) + MgH2 with 8.3 wt%, and NaBH4 + MgH2 with 7.8 wt%. (c) 2006 Elsevier B.V. All rights reserved.