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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Compositional effects on the hydrogen storage properties of Mg(NH_2)_2-2LiH-xKH and the activity of KH during dehydrogenation reactions
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Compositional effects on the hydrogen storage properties of Mg(NH_2)_2-2LiH-xKH and the activity of KH during dehydrogenation reactions

机译:组成对Mg(NH_2)_2-2LiH-xKH的储氢性能和脱氢反应中KH活性的影响

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摘要

Potassium hydride (KH) was directly added to a Mg(NH_2)_2-2LiH system to improve the hydrogen storage properties; the corresponding mechanisms were elucidated. The Mg(NH_2)_2-2LiH-0.08KH composite displays optimized hydrogen-storage properties, reversibly storing approximately 5.2 wt% hydrogen through a two-stage reaction and a dehydrogenation onset at 70 °C. The 0.08KH-added sample fully dehydrogenated at 130 °C begins to absorb hydrogen at 50 °C, and takes up approximately 5.1 wt% of hydrogen at 140 °C. Adding KH significantly enhances the de-/hydrogenation kinetic properties; however, an overly rapid hydrogenation rate enlarges the particle size and raises the dehydrogenation temperature. A cycling evaluation reveals that the KH-added Mg(NH_2)_2-2LiH system possesses good reversible hydrogen storage abilities, although the operational temperatures for de-/hydrogenation increase during cycling. Detailed mechanistic investigations indicate that adding KH catalytically decreases the activation energy of the first dehydrogenation step and reduces the enthalpy of desorption during the second dehydrogenation step as a reactant, significantly improving the hydrogen storage properties of Mg(NH_2)_2-2LiH.
机译:将氢化钾(KH)直接添加到Mg(NH_2)_2-2LiH系统中以提高储氢性能;阐明了相应的机制。 Mg(NH_2)_2-2LiH-0.08KH复合材料显示出优化的储氢性能,可通过两步反应和70°C的脱氢反应可逆地存储约5.2 wt%的氢。在130°C下完全脱氢的添加0.08KH的样品在50°C下开始吸收氢,并在140°C下吸收约5.1 wt%的氢。添加KH显着增强了脱氢/氢化动力学性能。但是,过快的氢化速度会增大粒径并提高脱氢温度。循环评价表明,尽管在循环过程中脱氢/加氢的操作温度升高,但添加KH的Mg(NH_2)_2-2LiH体系具有良好的可逆储氢能力。详细的机理研究表明,添加KH可以催化降低第一脱氢步骤的活化能,并降低第二脱氢步骤中作为反应物的解吸焓,从而显着提高Mg(NH_2)_2-2LiH的储氢性能。

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