Crystallographic analysis of hydrogen clathrate hydrates in confined nanospace

Clathrate hydrates are some of the most exciting crystalline structures in nature. Under favourable pressure and temperature conditions, water molecules can be arranged in a 3D hydrogen bonded network, giving rise to spaces or cages in the size range of many gas molecules. A critical limitation of hydrates is their slow nucleation and growth kinetics due to the limited gas-H2O interface in bulk conditions, but previous studies from our research group have demonstrated that specially designed porous materials can surpass these obstacles by acting as nanoreactors promoting the nucleation and growth of gas clathrates. The confinement effects in the inner cavities promote their massive growth at moderate temperatures, using pure water, with extremely fast kinetics and at much lower pressures than the bulk system. From previous low-resolution diffraction data, we know that H2 clathrates grow in the cavities of PPAC activated carbon at pressures above 135 MPa. This development could be a breakthrough that will make hydrogen clathrates a viable hydrogen storage technology. The main goal of this proposal will be to evaluate the hydrogen clathrate growth at two different pressures, 135 MPa and 200 MPa, to locate the crystallographic sites of hydrogen molecules in the small and large cavities of the clathrate and follow their stability as a function of temperature.