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化学学报
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化学学报 ›› 2008, Vol. 66 ›› Issue (9): 1037-1041. 上一篇    下一篇

研究论文

Ti掺杂的MgH2和Mg2NiH4的放氢性能

周广有1，郑时有1，方方1，张晶1，徐芬2，孙立贤2，陈国荣1，孙大林*,1   

  1. (1复旦大学材料科学系 上海 200433)
    (2中国科学院大连化学物理研究所 大连 116023)
  • 投稿日期:2007-07-01 修回日期:2007-10-28 发布日期:2008-05-14
  • 通讯作者: 孙大林

Hydrogen Desorption Performance of Ti-Mediated MgH2 and Mg2NiH4

ZHOU Guang-You1 ZHENG Shi-You1 FANG Fang1 ZHANG Jing1 XU Fen2 SUN Li-Xian2 CHEN Guo-Rong1 SUN Da-Lin*1   

  1. (1 Department of Material Science, Fudan University, Shanghai 200433)
    (2 Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023)
  • Received:2007-07-01 Revised:2007-10-28 Published:2008-05-14
  • Contact: SUN Da-Lin

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以TiF3和Ti(OBu-n)4为催化剂, 研究了Ti离子掺杂对MgH2和Mg2NiH4放氢性能的影响. 结果表明, 未掺杂的MgH2起始放氢温度为420 ℃, 掺杂TiF3和Ti(OBu-n)4后分别降低到360和410 ℃; Mg2NiH4在掺杂TiF3后放氢温度由230 ℃降低到220 ℃, 而掺杂Ti(OBu-n)4后没有变化. 可见无论对MgH2或Mg2NiH4, 在降低放氢温度方面TiF3都明显优于Ti(OBu-n)4. 另外, 研究还发现, TiF3掺杂对MgH2放氢动力学有显著的提高, 但对Mg2NiH4没有明显的提高. 结合XRD和FTIR的测试分析, 我们认为: 催化作用很大程度上取决于氢化物自身的晶体结构和催化剂的电子结构; 降低氢化物放氢温度和提高动力学性能的原因是催化剂与氢化物之间的相互作用削弱了氢化物中Mg—H或Ni—H键, 使得活泼的H…H原子对容易形成, 从而有利于H2的释出.

关键词: Ti掺杂, 放氢性能, MgH2, Mg2NiH4

TiF3 and Ti(OBu-n)4-doped MgH2 and Mg2NiH4 were investigated with regard to hydrogen desorption performance. It was found that the onset temperature for hydrogen release was around 420 ℃ for the blank MgH2, but decrease to 360 and 410 ℃ for the TiF3- and the Ti(OBu-n)4-doped MgH2, respectively. For Mg2NiH4, it was reduced from 230 to 220 ℃ after doping with TiF3, but remained unchanged once doping with Ti(OBu-n)4. These indicate that TiF3 is more efficient than Ti(OBu-n)4 in reducing the stability of MgH2 and Mg2NiH4. The enhanced desorption kinetics is attained in the TiF3-doped MgH2, but not in the TiF3-doped Mg2NiH4. Combined with XRD and FTIR techniques, the catalytic activity was thought to be jointly influenced by the crystal structure of the hydride and the electronic structure of the catalyst. The decrease in hydrogen release temperature and the improvement in kinetics are owing to the weakening of the Mg(Ni)—H bonds through the interactions between the catalyst and the hydride, thus facilitating energetically the formation of intra-H…H pairings that further recombine readily towards the molecular hydrogen.

Key words: Ti doping, hydrogen desorption, MgH2, Mg2NiH4