SusChEM: Structural and Mechanistic Insights into the Enhanced Hydrogen Sorption Properties of Metal Hydride Nanoparticles Made via Solution Reactions

氢气是汽车和其他便携式应用的理想燃料，因为它在空气中清洁燃烧，唯一的副产品是水。 它还具有非常高的能量密度，几乎是汽油的三倍。 然而，使用氢作为燃料的主要挑战是其清洁生产和储存。 将氢气以气体形式储存需要大型气瓶，而将其以液体形式储存需要高压和极低的温度。这两种方法也带来了安全挑战。 普列托博士正在探索使用固体化合物作为氢的储存材料。 这种方法在合理的压力下提供小的存储体积。 轻金属镁等金属镁每单位质量可以储存大量的氢，但缺点是将氢放入镁中需要高温和高压，而除去氢需要高温和低压。 这两个过程都非常缓慢。 普列托博士和她的学生设计了一种制造非常小的镁颗粒的方法，这种颗粒显示出更快的储氢速度。 她的工作目标是确定在镁表面添加少量其他金属是否可以进一步增加添加或从金属颗粒中去除氢的速率。 她使用X射线衍射，热分析，固态核磁共振和X射线吸收实验等技术来帮助模拟氢化反应的速率，并提供有助于开发动力学模型来描述这些反应的数据。 普列托涉及从高中到研究生水平的学生在她的研究，这项工作的实际应用作为一个有用的招聘工具，以吸引有才华的学生，并培养他们的研究，旨在提高能源的可持续性。 普列托通过她作为科罗拉多清洁能源集群的董事会成员的角色向公众传达她对氢存储和能源可持续性的知识，该集群直接影响科罗拉多的经济发展政策和与清洁能源生产，存储和运输相关的项目。 该项目被用作基础研究的一个例子，可以很容易地与广泛受众感兴趣的应用相联系，即清洁能源生产和储存。氢气是便携式应用的理想燃料，因为它在空气中清洁燃烧产生水，并且它具有非常高的能量密度。 镁（Mg）、掺杂的Mg和Mg合金由于其高的理论储氢容量（例如MgH2为7.6重量%）而成为有前景的储氢材料。然而，由于氢吸收和解吸所需的缓慢动力学和高温，块状Mg作为储氢材料不太理想。Prieto博士正在合成储氢材料的纳米颗粒，其中减小的尺寸导致储氢动力学显著增强。 她正在确定动力学和热力学对这些颗粒的氢吸附和解吸的相对作用，特别是在向表面添加少量过渡金属时。虽然纳米级金属氧化物的氢化速率更快，但对表面积增加与杂质和缺陷的作用知之甚少。普列托博士正在研究的目标是地球上丰富的元素，这些元素很轻，可以储存大量的氢，尽管它们的体积很小。通过控制颗粒尺寸和添加剂类型和位置，她可以显著提高在本体中观察到的缓慢氢化速率，并最终能够降低这些材料氢化所需的温度。 这项研究的结果是招募和留住了一批有才华的、多样化的学生。

Hydrogen is an ideal fuel for vehicles and other portable applications because it burns cleanly in air and the only byproduct is water. It also has a very high energy density, almost three times higher than gasoline. The main challenges to using hydrogen as a fuel, however, are its clean production and storage. Storing hydrogen as a gas requires large cylinders, and storing it as a liquid requires high pressures and very low temperatures. Both methods also present safety challenges. Dr. Prieto is exploring the use of solid compounds as storage materials for hydrogen. This approach offers small storage volumes at reasonable pressures. Light metal hydrides, such as magnesium metal, can store a lot of hydrogen per unit mass, but the drawbacks are that putting the hydrogen into magnesium requires high temperatures and pressures, and removing the hydrogen requires high temperatures and low pressures. Both processes are very slow. Dr. Prieto and her students have designed a method of making very small particles of magnesium that display much faster rates for storing hydrogen. The goal of her work is to determine whether the addition of small amounts of other metals to the surface of the magnesium can further increase the rates of adding or removing the hydrogen from the metal particles. She uses techniques such as X-ray diffraction, thermal analysis, solid state nuclear magnetic resonance, and X-ray absorption experiments to help model the rates of the hydrogenation reactions and to provide data that aid in developing kinetic models to describe these reactions. Dr. Prieto involves students ranging from high school to graduate levels in her research, and the practical applications of this work serve as a useful recruiting tool to attract talented students and train them in research aimed at improving energy sustainability. Prof. Prieto communicates her knowledge of hydrogen storage and energy sustainability to the general public through her role as a board member of the Colorado Clean Energy Cluster, which is directly impacting policy in Colorado for economic development and projects related to clean energy production, storage, and transportation. This project is used as an example of basic research that can be easily linked to an application interesting to a wide audience, that of clean energy production and storage. Hydrogen is an ideal fuel for portable applications because it burns cleanly in air to produce water, and it has a very high energy density. Magnesium (Mg), doped Mg, and Mg alloys are promising materials for hydrogen storage due to their high theoretical hydrogen storage capacities (e.g. 7.6 weight% for MgH2). However, bulk Mg is less than ideal as a hydrogen storage material due to the slow kinetics and high temperatures required for hydrogen absorption and desorption. Dr. Prieto is synthesizing nanoparticles of hydrogen storage materials in which the reduced size results in significantly enhanced kinetics for hydrogen storage. She is determining the relative roles of kinetics and thermodynamics on the hydrogen sorption and desorption of these particles, particularly upon addition of small amounts of transition metals to the surface. Although faster hydrogenation rates have been observed for nanoscale metal hydrides, very little is known about the roles of increased surface area versus impurities and defects. The targets Dr. Prieto is studying are earth abundant elements that are light and store large amounts of hydrogen, albeit sluggishly in the bulk. With control over the particle size and additive type and position, she can dramatically increase the slow hydrogenation rates observed in the bulk and, ultimately, be able to lower the temperature required for hydrogenation of these materials. This research results in recruiting and retaining a talented, diverse group of students.