The dehydrogenation kinetics and reversibility improvements of Mg(BH4)2 doped with Ti nano-particles under mild conditions |
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| Authors: | Xuancheng Wang Xuezhang Xiao Jiaguang Zheng Zhouming Hang Wenping Lin Zhendong Yao Meng Zhang Lixin Chen |
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| Affiliation: | 1. State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China;2. Zhejiang University of Water Resources and Electric Power, Hangzhou 310018, China;3. Key Laboratory of Advanced Materials and Applications for Batteries of Zhejiang Province, Hangzhou 310013, China |
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| Abstract: | Magnesium borohydride, Mg(BH4)2, is ball-milled with Ti nano-particles. Such catalyzed Mg(BH4)2 releases more hydrogen than pristine Mg(BH4)2 does during isothermal dehydrogenation at 270, 280, and 290 °C. The catalyzed Mg(BH4)2 also exhibits better dehydrogenation kinetics than the pristine Mg(BH4)2. Based on kinetics model fitting, the activation energy (Ea) of the catalyzed Mg(BH4)2 is calculated to be lower than pristine Mg(BH4)2. During partial dehydrogenation, the catalyzed Mg(BH4)2 releases 4.23 wt % (wt%) H2 for the second dehydrogenation at 270 °C, comparing to 4.05, and 3.75 wt% H2 at 280, and 290 °C. The reversibility of 4.23 wt% capacity is also one of the highest for Mg(BH4)2 dehydrogenation under mild conditions such as 270 °C as reported. 4 cycles of Mg(BH4)2 dehydrogenation are conducted at 270 °C. The capacities degrade during 4 cycles and tend to be stable at about 3.0 wt% for the last two cycles. By analyzing the hydrogen de/absorption products of the catalyzed sample, Mg(BH4)2 is found to be regenerated after rehydrogenation according to Fourier Transform Infrared (FTIR) spectroscopy. Ti nano-particles can react with Mg(BH4)2 during ball-milling and de/rehydrogenation. The products include TiH1.924, TiB, and TiB2, which can improve the dehydrogenation properties of Mg(BH4)2 from a multiple aspect. |
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| Keywords: | Magnesium borohydride Ti Hydrogen storage Kinetics Reversibility |
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