Investigation of the anhydrous molten Na-B-O-H system and the concept: Electrolytic hydriding of sodium boron oxide species
Investigation of the anhydrous molten Na-B-O-H system and the concept: Electrolytic hydriding of sodium boron oxide species
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DOI：
10.1016/j.jpowsour.2006.11.023
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发表时间：
2007-02-10
影响因子：
9.2
通讯作者：
Davis, Boyd R.
中科院分区：
文献类型：
--
作者：
Calabretta, Daniel L.;Davis, Boyd R.
虽然硼氢化钠（NaBH 4）可以作为一种优异的储氢材料，但其成本使其在汽车应用中不切实际。本文介绍了偏硼酸钠电解法制取硼氢化钠的概念。通过推导，我们断言，只有采用致密的固体氧化物离子电解质和含有这两种成分的熔融盐溶液，这样的过程才是可能的。以NaH、NaBO 2和NaBH 4为起始原料，采用压差热分析（PDTA）、X射线衍射（XRD）和析气分析（GEA）等方法对熔融无水Na-B-O-H体系进行了研究。我们发现，熔融NaBH 4与NaBO 2在600 ℃以上不稳定，这是由于形成原硼酸钠（Na 4 B2 O 5）、氢和硼。然而，所发现的准倒易三元系（4/5）NaH-NaBO 2-（1/5）NaBH 4-（2/5）Na 4 B2 O 5证明熔融Na 4 B2 O 5在本研究中使用的氢气压力下与熔融NaBH 4在至少650 ℃下是可混溶的且稳定的。此外，还发现了化合物Na_6B_3O_5H_2，并通过实验推导出了无水Na-B-O-H相图的相当一部分。在系统内存在大的离子液体组成域，其将允许待测试的硼氧化钠物质的电解沉积。(c)2006 Elsevier B. V.保留所有权利。
Although sodium borohydride (NaBH4) can act as an excellent hydrogen storage material, its cost renders it impractical for automotive applications. In this paper the concept of electrolytic production of NaBH4 from sodium metaborate (NaBO2) is introduced following a literature review of NaBH4 synthesis. By deduction, we assert that only by employing dense solid oxide ion electrolytes and a molten salt solution containing the two constituents would such a process be possible. We investigated the molten anhydrous Na-B-O-H system by pressure differential thermal analysis (PDTA), X-ray diffraction (XRD) and gas evolution analysis (GEA) using the starting reagents sodium hydride (NaH), NaBO2 and NaBH4. We found that molten NaBH4 is not stable with NaBO2 above 600 degrees C due to the formation of sodium orthoborate (Na4B2O5), hydrogen and boron. However, the quasi-reciprocal ternary system, (4/5)NaH-NaBO2-(1/5)NaBH4-(2/5)Na4B2O5, that was discovered, proves that molten Na4B2O5 is miscible and stable with molten NaBH4 to at least 650 degrees C under the hydrogen pressures used in this study. As well, the compound Na6B3O5H2 was discovered and a substantial portion of the anhydrous Na-B-O-H phase diagram has been experimentally deduced. There is a large ionic liquid composition domain within the system that would allow for the electrolytic hydriding of sodium boron oxide species to be tested. (c) 2006 Elsevier B.V. All rights reserved.