TEM-based approach for understanding microstructure-properties relations in hydrogen storing Mg-Ge-Ti and Mg-Ti-Ni nanocomposites

缺乏可接受的储氢介质是在移动的、手持的和固定的商业应用中允许燃料电池的广泛商业利用的关键缺失组分。镁具有固态储氢的前景，因为MgH 2中的氢含量相对较高（7.6wt.%）并且因为镁是廉价的。镁的关键问题是其不可接受的高充电和放电温度，这是由于氢化物形成的相对大的负热（~ 76 kJ/mol）。提出了开发Mg-Fe-Ti合金和Mg-Ti-Ni纳米储氢复合材料的设想。这些系统是有希望的候选者，因为可以使用在其无氢状态下形成的金属间化合物（两种或更多种元素的化合物，其中至少一种是金属）的能量来使生成热不那么负。我建议使用合金薄膜作为模型系统，以探索组成和微观结构在储氢性能中的作用。合金的设计方法将伴随着通过低温阶段的透射电子显微镜（TEM）的直接微观结构表征。这将使我们直接了解适当的吸附热力学和动力学所需的材料的特征。

The lack of an acceptable hydrogen storage media is a critical missing component in allowing for widespread commercial utilization of fuel cells in mobile, hand-held and stationary commercial applications. Magnesium has promise for solid-state hydrogen storage because of the relatively high amount of hydrogen held in MgH2 (7.6wt.%) and because magnesium is inexpensive. The critical problem with magnesium is its unacceptably high charging and discharging temperature due to a relatively large negative heat of hydride formation (-76 kJ/mol). I am proposing to develop alloy Mg-Fe-Ti and Mg-Ti-Ni hydrogen storage nanocomposites. These systems are promising candidates since it may be possible to use the energy of the intermetallics (compounds of two or more elements, where at least one is a metal) formed in their hydrogen-free state to make the heat of formation less negative. I am proposing using alloy thin films as model systems to explore the role of composition and microstructure in the hydrogen storage properties. The alloy design methodology will be accompanied by direct microstructural characterization via cryogenic-stage transmission electron microscopy (TEM). This will give us direct insight into the features of the material necessary for proper adsorption thermodynamics and kinetics.