Comparison of the Calculated and Experimental Scenarios for Solid-State Reactions Involving Ca(AlH4)2
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- 作者：Nobuko Hanada ; Wiebke Lohstroh ; Maximilian Fichtner
- 刊名：Journal of Physical Chemistry C
- 出版年：2008
- 出版时间：January 10, 2008
- 年：2008
- 卷：112
- 期：1
- 页码：131 - 138
- 全文大小：201K
- 年卷期：v.112,no.1(January 10, 2008)
- ISSN：1932-7455
文摘
Solid-state reactions of Ca(AlH4)2 and various additives were investigated experimentally for hydrogendesorption. The Ca(AlH4)2 + Si, Ca(AlH4)2 + 2MgH2, Ca(AlH4)2 + 2LiH, and Ca(AlH4)2 + 2LiNH2 systemswere chosen among reactions proposed theoretically1 to study their hydrogen storage capacity and an appropriatereaction enthalpy. For all systems investigated, the reversible reactions proposed should have more than 6.5mass % hydrogen capacity and reaction enthalpies in the range of 30-55 kJ/mol H2. However, most of theexperimentally observed reactions do not conform to theoretical propositions because different final productswere obtained in all cases but one. Two tendencies were observed in the experiments. One is that the reactioncomprises several distinct steps at different temperatures as observed in the Ca(AlH4)2 + Si and Ca(AlH4)2+ 2 MgH2 systems. In this case, Ca(AlH4)2 decomposes first and is followed by a reaction of the remainingcompounds. The same kinetic reaction barriers are encountered here as in pure Ca(AlH4)2. Second, LiH andLiNH2 additions yield exothermic reactions of Ca(AlH4)2 and the other reactant as early as in the ball millingor annealing steps, leading to final products not considered in the reactions calculated.