Abstract: Gas hydrates offer significant advantages for energy storage. Water is inexpensive, readily available and environmentally inert, however the hydrates of hydrogen and carbon dioxide which form close to ambient pressure do not hold sufficient proportions of gas. The application of pressure makes large changes to water networks. At ambient pressure there are two network topologies but the application of only 20 kbar accesses seven more which makes pressure a useful tool to search for new potential gas storage materials.
I will present recent investigations of the hydrogen-water system using neutron diffraction. These have identified a new hydrogen-hemihydrate as well as correctly identifying the structure and composition of a previously known phase. Related work on carbon-dioxide water has shown that this system has a structure in common with a hydrogen hemihydrate and that mixed carbon-dioxide hydrogen hydrates can be formed. I will also present work on ammonia hydrates which have potential as a basis for ionic network structures.