Hydrogen NMR of H2-TDF-D2O clathrate

The three-component clathrate H2-TDF-D2O offers hydrogen storage at lower pressure, but with reduced weight fraction of H2, compared to H2-H2O clathrate. In H2-TDF-D2O, H2 resides exclusively and singly in the small cages of structure II, allowing the rotational behavior of H2 in this nominally uniform environment to be probed. Here we report NMR measurements of the H2 line shape and relaxation times T1, T2, and T1rho. The principal differences in the results, compared to the H2-D2O binary system, are the dips in T2 and T1rho near 28 K due to thermally activated reorientation of TDF molecules, line-narrowing and decreases in T2 and T1rho near 175 K due to D2O reorientations and diffusion, and the apparent absence of H2 diffusion between small cages.