Preparations and de/re-hydrogenation properties of LixNa3-xAlH6 (x=0.9-1.3) non-stoichiometric compounds
Preparations and de/re-hydrogenation properties of LixNa3-xAlH6 (x=0.9-1.3) non-stoichiometric compounds
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LixNa3-xAlH6 (x=0.9-1.3)非化学计量化合物的制备及脱/再氢化性能
DOI：
10.1016/j.jallcom.2017.09.205
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发表时间：
2017
影响因子：
6.2
通讯作者：
Li Liquan
中科院分区：
文献类型：
--
作者：
Fan Xiaolu;Zhang Yao;Zhu Yunfeng;Phillips Cass;ra;Guo Xinli;Chen Jian;Wang Zengmei;Li Liquan
通过研磨特定摩尔比的Li3AlH6和Na3AlH6混合物，成功合成了混合碱金属铝酸盐LixNa3-xAlH6。具有单一钙钛矿型结构（空间群Fm-3m）的非化学计量LixNa3-xAlH6化合物只能在x = 0.9–1.3的组成范围内形成。 Li1.3Na1.7AlH6 比其他 LixNa3-xAlH6 化合物表现出优异的储氢性能。在程序升温脱氢 (TPD) 曲线中，其起始脱氢温度 (∼423 K) 比其他样品降低了 40 K 以上。此外，Li1.3Na1.7AlH6(3.45 wt.%)的脱氢能力是化合物中最高的。根据等温压力-组成(PCI)曲线和van't Hoff图的结果，LixNa3-xAlH6的脱氢焓随着x从0.9增加到1.3而降低。结果表明，Li1.3Na1.7AlH6(49.7 kJ mol H2−1) 的脱氢反应比 LiNa2AlH6 (68.1 kJ mol H2−1) 的脱氢反应大大不稳定。此外，Li1.3Na1.7AlH6（138.1 kJ mol−1）的脱氢表观活化能显着低于LiNa2AlH6。这说明 Li1.3Na1.7AlH6 表现出比 LiNa2AlH6 增强的脱氢动力学。
Mixed alkali alanates LixNa3-xAlH6have been successfully synthesized by means of grinding mixtures of Li3AlH6and Na3AlH6in specific molar ratios. Non-stoichiometric LixNa3-xAlH6compounds with single perovskite-type structures (space group Fm-3m) can be formed only within the composition range of x = 0.9–1.3. Li1.3Na1.7AlH6exhibits superior hydrogen storage properties over other LixNa3-xAlH6compounds. Its onset dehydrogenation temperature (∼423 K) was lowered by more than 40 K from other samples in temperature programmed dehydrogenation (TPD) curves. Also, the dehydrogenation capacity of Li1.3Na1.7AlH6(3.45 wt.%) is the highest among the compounds. The dehydrogenation enthalpy values of LixNa3-xAlH6decreased as x increased from 0.9 to 1.3 according to the results by isothermal pressure-composition (PCI) curves and van't Hoff plots. It shows that the dehydrogenation Li1.3Na1.7AlH6(49.7 kJ mol H2−1) was greatly destabilized from that of LiNa2AlH6(68.1 kJ mol H2−1). Furthermore, the apparent activation energy of dehydrogenation for Li1.3Na1.7AlH6(138.1 kJ mol−1) was remarkably lowered from that of LiNa2AlH6. This illustrates that Li1.3Na1.7AlH6exhibits enhanced dehydrogenation kinetics from that of LiNa2AlH6.