Hydrogen storage in molecular clathrates

Clathrate materials have the potential for future energy applications especially for hydrogen-fueled cars, energy storage and distribution grids. They have great potential as molecular hydrogen storage (MHS) in hydrocarbons. Clathrates are two or more components that are associated without ordinary chemical union but through complete enclosure of one set of molecules in a suitable structure formed by another. They are cage-like host-guest structure and can yield different forms from water molecules due to their tetrahedral coordination and hydrogen bonding topology determined by the ice rules. Guest molecules can be accommodated only in the larger cages depending on their size. The most extensively studied clathrates are hydrates which are defined by diffraction methods at atmospheric pressure and low temperature. The kinetics of clathrate formation can be affected by different synthesis routes. Hydrogen clathrate is seen as attractive because it is a clean and inexpensive storage material since the only byproduct after release of the stored molecular hydrogen is water. In ternary systems, the properties of clathrate hydrates may differ from those with one type of guest molecule as well as small impurities of another gas which changes the structure of the clathrate hydrate formed. So far, the only structure known to accommodate hydrogen at low pressures in the sII clathrate structure. There are at present efforts in the search for more complex structures.