Hydrogen can be stored in three states:
- As a pressurised gas, with pressures up to 700 bars.
- As a liquid, in cryogenic tanks (vacuum insulation)
- In solids such as metal hydrids (chemical compounds of hydrogen and metal), metal organic frameworks (porous materials) or on the surface of carbon nanotubes or nanocones (newly discovered compounds)
Metal hydrides are very promising media for hydrogen storage because of the high volumetric density of hydrogen along with the ability to store hydrogen at atmospheric pressure at room temperature. Hydrogen storage in metal hydrides is particulary interesting in conjunction with small and mobile storage units and batteries.
An important task is to understand how metal hydrides are formed, so that new types of metal hydrides with improved properties can be synthesises for various purposes. The hydrogenation properties, i.e. the ability to take up and release hydrogen,
vary from element to element. By mixing the right elements into new compunds, the properties of metal hydrides can be optimized for a high hydrogen uptake and release at moderate conditions.
Beams of neutron, X-ray and electron beams are most often used to investigate the structure of new materials. These methods offer a way to observe the inside of a material on the atomic scale.
Worldwide there is vigorous research on the field of metal hydrides. IFE has had a significant presence in this field since the 1950s.