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允许燃料电池在移动、手持和固定商业应用中广泛商业使用的关键缺失部分。镁具有固态氢存储的前景，因为氢氧化镁中的氢含量相对较高(7.6wt.%)，而且镁的价格也不高。镁的关键问题是，由于氢化物形成的负热相对较大(-76kJ/mol)，镁的充放电温度高得令人无法接受。我建议开发合金镁-铁-钛和镁-钛-镍储氢纳米复合材料。这些体系是很有希望的候选者，因为有可能利用在无氢状态下形成的金属间化合物(两个或更多元素的化合物，其中至少一个是金属)的能量来降低生成热的负值。我建议使用合金薄膜作为模型系统来探索成分和微观结构在储氢性能中的作用。合金设计方法将伴随着通过低温阶段透射电子显微镜(TEM)直接进行微观结构表征。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.