Effect of Molecular Nitrogen on Multiple Hydrogen Occupancy in Clathrate Hydrates

Multiple H-2 occupancy in confined cages has been explored for the purpose of enhancing storage capacity. Furthermore, balancing the formation pressure with high storage capacity is one of the most significant factors. Here, we demonstrate the use of binary (LGM + N-2) hydrates to capture hydrogen clusters under relatively mild conditions, even observing double H-2 occupancy in small cages. The cage occupancy and structures of hydrates were identified by the Raman spectroscopic analysis and high-resolution powder diffraction. The reaction product of binary (LGM + N-2) hydrates with H-2 molecules suggests the possibility of multiple H-2 occupancy in both small (5(12)) and large (5(12)6(4)) cages at relatively low pressures. Also, the lattice parameter decreases with an increase in H-2 occupancy. The unique and abnormal role of N-2 as a preoccupied coguest significantly affects the H-2 population in a crystalline hydrate matrix and further lowers the pressure for structure stabilization.