Hydrogen Storage Materials Thesis Statements


Reference:

Sharpe, J., 2015. Modelling Hydrogen Storage in Nanoporous Materials for use in Aviation. Thesis (Doctor of Philosophy (PhD)). University of Bath.

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Abstract

There is a growing need for new sources of energy due to the rise in global energy demand, the decline in fossil fuels, and the increasing, negative consequences of climate change. Renewable energy resources are sustainable but they are also intermittent, meaning that they cannot supply energy on demand unless it is stored. Hydrogen is one potential chemical method of storing this energy; however, it has a very low energy density per unit volume, meaning that storage in low mass and volume containers can be problematic. One solution is to adsorb hydrogen onto highly porous materials. This thesis presents an improved methodology for analysing hydrogen adsorbed inside porous materials, and how it can be utilised to determine the potential use of storing hydrogen via physisorption for aviation. Preliminary studies are conducted on pressure and temperature dependencies of both the pore volume and the adsorbate density, and a comparison is also made between the utilisation of different Type 1 isotherms for the fractional filling of hydrogen, with the use of the Tόth equation resulting in the best quality of fit to the isotherms overall. The model is verified using inelastic neutron scattering and computer simulations. The model is then utilised to calculate the amount of hydrogen within a tank containing varying quantities of adsorbent, and comparing this to the amount of hydrogen that can be stored via direct compression at the same conditions. This is then expanded to be compared to alternative energy systems, and a preliminary investigation on the use of adsorbed hydrogen within aviation is conducted. The results show hydrogen adsorption to always have a higher energy density than compressed hydrogen up to a certain pressure, and for both to have a comparable energy density to battery storage at certain conditions, but not to standard jet fuels.

Item TypeThesis (Doctor of Philosophy (PhD))
CreatorsSharpe, J.
DepartmentsFaculty of Engineering & Design > Chemical Engineering
Publisher StatementJessica_Sharpe_thesis_final.pdf: © The Author
StatusPublished
ID Code43024

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Benge, K. R. (2008). Hybrid Solid-State Hydrogen Storage Materials (Thesis, Master of Science (MSc)). The University of Waikato, Hamilton, New Zealand. Retrieved from https://hdl.handle.net/10289/2320

Abstract
This thesis investigates the chemistry of ammonia borane (NH3BH3) relevant to the development of hydrogen storage systems for vehicular applications.Because of its high hydrogen content and low molecular weight ammonia borane has the potential to meet stringent gravimetric hydrogen storage targets of gt;9 wt%. Two of the three moles of H2 in ammonia borane can be released under relatively mild conditions, with the highest gravimetric yield obtained in the solid-state. However, ammonia borane does not deliver sufficient H2 at practical temperatures and the products formed upon H2 loss are not amenable to regeneration back to the parent compound.The literature synthesis of ammonia borane was modified to facilitate large scale synthesis, and the deuterated analogues ND3BH3 and NH3BD3 were prepared for the purpose of mechanistic studies.The effect of lithium amide on the kinetics of dehydrogenation of ammonia borane was assessed by means of solid-state reaction in a series of specific molar ratios. Upon mixing lithium amide and ammonia borane, an exothermic reaction ensued resulting in the formation of a weakly bound adduct with anH2N...BH3-NH3 environment. Thermal decomposition at or above temperatures of 50eg;C of this phase was shown to liberate gt;9 wt% H2. The mechanism of hydrogen evolution was investigated by means of reacting lithium amide and deuterated ammonia borane isotopologues, followed by analysis of the isotopic composition of evolved gaseous products by mass spectrometry. From these results, an intermolecular multi-step reaction mechanism was proposed, with the rates of the first stage strongly dependent on the concentration of lithium amide present. Compounds exhibiting a BN3 environment (identified by means of solid-state sup1;sup1;B NMR spectroscopy) were formed during the first stage, and subsequently cross link to form a non-volatile solid. Further heating of this non-volatile solid phase ultimately resulted in the formation of crystalline Li3BN2 - identified by means of powder X-ray diffractometry. This compound has been identified as a potential hydrogen storage material due to its lightweight and theoretically high hydrogen content. It may also be amenable to hydrogen re-absorption.The LiNH2/CH3NH2BH3 system was also investigated. Thermal decomposition occurred through the same mechanism described for the LiNH2/NH3BH3 system to theoretically evolve gt;8 wt% hydrogen. The gases evolved on thermal decomposition were predominantly H2 with traces of methane detected by mass spectrometry.

Date
2008

Publisher

The University of Waikato

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