Improved Hydrogen Storage Properties of NaBH4 Destabilized by CaH2 and Ca(BH4)2

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• 作者：Jianfeng Mao ; Zaiping Guo ; Xuebin Yu ; Huakun Liu
• 刊名：Journal of Physical Chemistry C
• 出版年：2011
• 出版时间：May 12, 2011
• 年：2011
• 卷：115
• 期：18
• 页码：9283-9290
• 全文大小：970K
• 年卷期：v.115,no.18(May 12, 2011)
• ISSN：1932-7455

文摘

NaBH₄, with a 10.6 wt % theoretical H₂ capacity, is a promising hydrogen storage candidate material. However, the high thermodynamic stability and slow H-exchange kinetics have to be improved for its practical use. In this study, NaBH₄ was destabilized by using CaH₂ or Ca(BH₄)₂. Temperature-programmed desorption experiments revealed a significant improvement in the decomposition temperature and the rate of desorption, as well as the weight percentage of hydrogen released from composites with the additive upon heating to 500 掳C. X-ray diffraction has confirmed the formation of CaB₆ upon dehydrogenation, which stabilizes the dehydrogenated state of boron and, therefore, destabilizes the NaBH₄. Interestingly, as a source of CaH₂, the addition of Ca(BH₄)₂ results in superior hydrogen desorption performance compared with that of CaH₂. To fully characterize this composite system, xNaBH₄ + Ca(BH₄)₂ composites, for several x values between 1 and 20, were systematically investigated by a series of dehydrogenation and structural analyses. Furthermore, partial reversibility of the NaBH₄/Ca(BH₄)₂ composite with and without NbF₅ catalyst was also confirmed under moderate conditions. The mechanism underlying the characteristic enhancement in the NaBH₄/CaH₂ and NaBH₄/Ca(BH₄)₂ is also discussed.