Metal Hydride Confinement in Functionalized Porous Hosts: Tuning Hydrogen Release Thermodynamics and Kinetics

安全能源储存是能源从化石能源和核能向可持续能源过渡的新挑战之一。人们追求不同的能量存储策略，例如在电池中存储电能或以氢的化学形式存储能量。储存氢的常用方法是通过吸附在多孔材料上或作为金属氢化物。金属氢化物因其重氢含量高而具有广阔的应用前景，但有些材料的反应动力学不可行，脱附焓高。为了调整这些性质，已经采取了一些方法，包括添加催化剂或在多孔宿主体内进行纳米限制。特别是后者显示出一些有希望的结果，因为氢化物与多孔宿主之间的主客体相互作用(1)实质性地改变了解吸动力学和热力学(2)稳定了小氢化物颗粒。此外，研究还表明，杂原子在宿主基质中形成lewis酸- lewis碱配合物的能力调整了金属氢化物颗粒的表面，并显著改变了氢的脱附性能。在这个项目中，目标是(1)在功能化多孔主体复合材料上制备金属氢化物，(2)用原位方法对其进行全面分析，最后(3)建立新的储氢材料的设计规则。该计划的第一部分将集中于在含有官能团的多孔宿主系统中制备不同的氢化物，这些将包括B和n掺杂的多孔碳，吡啶和含有氨基的功能化金属有机框架以及基于硼氧嘧啶和三嗪的共价有机框架。这些宿主将根据相关文献制备，其功能位点的含量将由合成条件控制。然后，制备的宿主材料将装载一系列氢化物，并将被充分表征。该项目的第二部分将集中于所制备的复合材料的（原位）表征，特别是反应途径和中间体的鉴定。将用于这项任务的方法是环境压力XPS，原位x射线吸收光谱和扫描透射x射线显微镜。最后，根据本研究项目前两个阶段的结果，设想建立新的储氢材料的设计规则。为此，将使用最有前途的复合材料（关于重量氢含量和解吸焓）作为起点。此外，该工作包将得到劳伦斯利弗莫尔国家实验室和桑迪亚国家实验室HyMARC集群合作伙伴的理论建模支持。

Safe Energy storage is one of the emerging challenges of the energy transition from fossil and nuclear energy towards sustainable energy. Different strategies to store energy are pursued, for instance electrical storage in batteries or chemically in the form of hydrogen. Common approaches to store hydrogen are either by adsorption on porous materials or as metal hydrides. Metal hydrides are promising due to their high gravimetric hydrogen content, however some materials show, unfeasible reaction kinetics and high desorption enthalpies. To tune these properties some approaches have been made, including the addition of catalysts or the nanoconfinement in porous host. In particular, the latter displayed some promising results as the host-guest interactions between hydride and porous host (1) alter the desorption kinetics and thermodynamics substantially and (2) stabilize small hydride particles. Moreover, it was shown that inclusion of heteroatoms into host matrices with the ability to form lewis acid – lewis base complexes tuned the surface of metal hydride particles and significantly altered the hydrogen desorption properties. Within this project the aim is to (1) prepare metal hydride at functionalized porous host composites, (2) fully analyze them with in-situ methods and finally (3) to establish rules for the design of new hydrogen storage materials.The first part of the proposed project will focus on the preparation of different hydride at porous host systems incorporating functional groups, these will include B- and N-doped porous carbons, pyridine and amino containing functionalized metal-organic frameworks as well as boroxine- and triazine-based covalent-organic frameworks. These hosts will be prepared according to the pertinent literature and their content of functional sites will be controlled by the synthesis conditions. The prepared host materials will then be loaded with a range of hydrides and will be fully characterized.The second part of the proposed project will focus on the (in-situ) characterization of the prepared composites, in particular the identification of reaction pathways and intermediates. Methods that will be used for this task are ambient pressure XPS, in-situ X-ray Absorption Spectroscopy and Scanning Transmission X-ray Microscopy. Lastly, from the results found during the first two stages of this research project, it is envisioned to establish rules for the design of new hydrogen storage materials. For this, the most promising composite materials (regarding gravimetric hydrogen content and desorption enthalpies) will be used as a starting point. Furthermore, this work package will be supported with theoretical modelling from collaboration partners of the HyMARC cluster at Lawrence Livermore National Laboratories and Sandia National Laboratories.