experimental validation of dense crystalline phases of nanoconfined H2 at low pressures via neutron diffraction

The high volumetric density of solid hydrogen (H2) makes it an attractive method for efficient hydrogen fuel storage. However, solid phases of H2 only exist at exceedingly low temperatures (<15 K) or extremely high pressures (Mbar) limiting practical implementation. Recent experiments reveal that nanoconfinement effects in porous materials can manipulate the phase diagram H2, producing crystalline phases at elevated temperatures, and further suggest that below a threshold pressure, the nanoconfined H2 solids may be denser than the equivalent compressed H2 solid. These experiments will utilize a pressurized H2 gas dosing cell on GEM neutron powder diffractometer, to map out the low-pressure crystalline phase diagram of hydrogen stabilized in nanoporous materials and determine if confined crystal densities are denser than the bulk equivalent at low-pressures. Both H2 and D2 will be examined to determine if any isotope effects infer differences between nanoconfined crystals and increase the scattering signal at low pressures/concentrations.