Evaluation of the hydrogen-storage capacity of pure H2 and binary H2-THF hydrates with Monte Carlo simulations

Grand Canonical Monte Carlo simulations are employed to investigate the hydrogen-storage capacity of pure H-2 and binary H-2-THF hydrates (both of them are of sII type) at various temperatures, pressures, and THF concentrations. It is found that the storage capacity of pure H-2 hydrate could reach 3.0 wt % only at pressures above 380 MPa (at 274 K). Depending on the pressure, the large cavities of this hydrate can accommodate up to four H-2 molecules, whereas the small ones are singly occupied even at pressures as high as 450 MPa. For the binary H-2-THF hydrate, all large cavities are found to be occupied by a single THF molecule, independent of the THF concentration in the initial solution in a wide range of conditions, with no hydrogen molecules entering the large cavities. Likewise, in the pure H-2 hydrate, small cavities are found to be singly occupied over the entire pressure range considered (1-350 MPa). The H-2 storage capacity of the binary H-2-THF hydrate, at temperatures close to ambient, is estimated to be lower than 1.1 wt %.