Complex Ammine Titanium(III) Borohydrides as Advanced Solid Hydrogen-Storage Materials with Favorable Dehydrogenation Properties

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• 作者：Feng Yuan ; Qinfen Gu ; Xiaowei Chen ; Yingbin Tan ; Yanhui Guo ; Xuebin Yu
• 刊名：Chemistry of Materials
• 出版年：2012
• 出版时间：September 11, 2012
• 年：2012
• 卷：24
• 期：17
• 页码：3370-3379
• 全文大小：614K
• 年卷期：v.24,no.17(September 11, 2012)
• ISSN：1520-5002

文摘

Ammine metal borohydrides (AMBs), with high hydrogen contents and favorable dehydrogenation properties, are receiving intensive research efforts for their potential as hydrogen storage materials. In this work, we report the successful synthesis of three ammine titanium borohydrides (denoted as ATBs), Ti(BH₄)₃路5NH₃, Li₂Ti(BH₄)₅路5NH₃, and Ti(BH₄)₃路3NH₃ via metathesis reaction of metal chloride ammoniates (TiCl₃路5NH₃ and TiCl₃路3NH₃) and lithium borohydride. These ATBs present favorable stability, owing to the coordination with NH₃ groups, compared to the unstable Ti(BH₄)₃ at room temperature. Dehydrogenation results revealed that Ti(BH₄)₃路5NH₃, which theoretically contains 15.1 wt % hydrogen, is able to release 13.4 wt % H₂ plus a small amount of ammonia. This occurred via a single-stage decomposition process with a dehydrogenation peak at 130 掳C upon heating to 200 掳C. For Li₂Ti(BH₄)₅路5NH₃, a three-step decomposition process with a total of 15.8 wt % pure hydrogen evolution peaked at 105, 120, and 215 掳C was observed until 300 掳C. In the case of Ti(BH₄)₃路3NH₃, a release of 14 wt % pure hydrogen via a two-step decomposition process with peaks at 109 and 152 掳C can be achieved in the temperature range of 60鈥?00 掳C. Isothermal TPD results showed that over 9 wt % pure hydrogen was liberated from Ti(BH₄)₃路3NH₃ and Li₂Ti(BH₄)₅路5NH₃ within 400 min at 100 掳C. Preliminary research on the reversibility of this process showed that dehydrogenated ATBs could be partly recharged by reacting with N₂H₄ in liquid ammonia. These aforementioned preeminent dehydrogenation performances make ATBs very promising candidates as solid hydrogen storage materials. Finally, analysis of the decomposition mechanism demonstrated that the hydrogen emission from ATBs is based on the combination reaction of B鈥揌 and N鈥揌 groups as in other reported AMBs.

Keywords:

hydrogen storage; ammine metal borohydrides; ammine titanium borohydrides; metathesis reaction