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

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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.