Dynamics of hydrogen molecules in the channels of binary THF-H2 clathrate hydrate and its physicochemical significance on hydrogen storage

We have studied the dynamics of the H2 loaded THF (tetrahydrofuran) clathrate hydrate by using an inelastic neutron scattering technique. At 2 K, a well defined single peak indicative of the ortho (J = 1) to para (J = 0) hydrogen transition is observed at 13.6 meV. The neutron spectrum undergoes two distinct changes as the temperature increases. First, additional peaks appear from splitting of the rotational transition above 10 K. Upon further heating, a quasi-elastic neutron scattering (QENS) signal due to hydrogen molecular diffusion through the THF hydrate crystalline lattice grows significantly above 65 K. These results indicate that H2 molecules trapped inside the THF hydrate crystalline structure undergo two distinct transformations in their dynamical behavior.