Towards a hydrogen-driven society? Calculations and neutron scattering on potential hydrogen storage materials

Towards a hydrogen-driven society? Calculations and neutron scattering on potential hydrogen storage materials

Schimmel, H.G.

Kearley, G.J. (promotor)

Applied Sciences

2005-02-01

For sustainable development, the resources of the earth need to be maintained and carbon dioxide emission should be avoided. In particular, we need to find an alternative for the use of fossil fuels in vehicles. Since long, hydrogen has been recognised as the fuel of the future because it exhausts only water when used in fuel cells and hardly any pollutants when used in conventional internal combustion engines. However, the storage of hydrogen onboard vehicles is a major concern. Hydrogen is a very light and volatile gas. Extremely low temperatures or very high pressures are needed to store a practical amount for vehicular use. Since these options are regarded to be expensive and unsafe, a material is sought that is capable of storing hydrogen in a reasonable amount at close-to-ambient conditions. In this thesis, we present two options for hydrogen storage in materials: 1) high surface area materials such as single walled carbon nanotubes and 2) metals such as magnesium. We conclude that hydrogen storage on single walled carbon nanotubes is very much similar to hydrogen storage in ordinary activated charcoals. From a fundamental point of view, however, there are some distinct differences due to the curved surfaces of the nanotubes. Regarding hydrogen storage in magnesium metal we showed that structural changes in magnesium due to a ball milling treatment are not of decisive importance for the resulting increase in hydrogen sorption speed. By in-situ neutron diffraction, a new phase was found in Nb-catalysed magnesium that might play an important role in the increase of the sorption speed. Finally we point out why heat effects and storage efficiencies should be taken into account for practical storage systems.

hydrogen storage
single walled carbon nanotubes
magnesium
neutron scattering
density functional theory
fuel cell
sustainable development

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doctoral thesis

(c) 2005 H.G. Schimmel