Hydrogen Storage Properties in (LiNH2)2-LiBH4-(MgH2)X Mixtures (X = 0.0-1.0)
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- 作者：Andrea Sudik ; Jun Yang ; Devin Halliday ; Christopher Wolverton
- 刊名：Journal of Physical Chemistry C
- 出版年：2008
- 出版时间：March 20, 2008
- 年：2008
- 卷：112
- 期：11
- 页码：4384 - 4390
- 全文大小：356K
- 年卷期：v.112,no.11(March 20, 2008)
- ISSN：1932-7455
文摘
We have recently reported the synthesis and properties of a novel hydrogen storage composition comprisedof a 2:1:1 molar ratio of three hydride compounds: lithium amide (LiNH2), lithium borohydride (LiBH4),and magnesium hydride (MgH2). This new ternary mixture possesses improved hydrogen (de)sorption attributes(relative to the individual compounds and their binary mixtures), including facile low-temperature kinetics,ammonia attenuation, and partial reversibility. Comprehensive characterization studies of its reaction pathwayrevealed that these favorable hydrogen storage properties are accomplished through a complex multistephydrogen release process. Here, we expound on our previous findings and determine the impact of MgH2content on the resulting hydrogen storage properties by examining a series of (LiNH2)2-LiBH4-(MgH2)Xreactant mixtures (i.e., 2:1:X molar ratio) where X = 0, 0.15, 0.25, 0.40, 0.50, 0.75, and 1.0. Specifically, wecharacterize each starting composition (after ball-milling) using powder X-ray diffraction (PXRD) and infraredspectroscopy (IR) and find that addition of MgH2 facilitates a spontaneous milling-induced reaction, introducingnew species (Mg(NH2)2 and LiH) into the hydride composition. We additionally measure the relative hydrogenand ammonia release amounts for each mixture using temperature-programmed desorption mass spectrometry(TPD-MS) and find that ammonia liberation is suppressed for increasing values of X (<0.1 wt % NH3 forX = 1). Kinetic hydrogen desorption data reveal a low-temperature reaction step (centered at ~160 
C) forall MgH2-containing samples which grows in intensity for larger values of X (up to ~4.0 wt % H2 for X =1). Finally, we characterize desorbed samples to investigate the dependence of X (MgH2 amount) on theresulting distribution of observed product phases. These data are used to understand how MgH2 contributesto and impacts the low- and high-temperature hydrogen release events through comparing theoretical (basedon the previously proposed reaction set) and observed desorption data for these reactions.
C) forall MgH2-containing samples which grows in intensity for larger values of X (up to ~4.0 wt % H2 for X =1). Finally, we characterize desorbed samples to investigate the dependence of X (MgH2 amount) on theresulting distribution of observed product phases. These data are used to understand how MgH2 contributesto and impacts the low- and high-temperature hydrogen release events through comparing theoretical (basedon the previously proposed reaction set) and observed desorption data for these reactions.