Monte Carlo study of sI hydrogen hydrates

In this study, we perform grand canonical Monte Carlo simulations to evaluate the hydrogen storage capacity of structure I (sI) hydrogen hydrates at pressures up to 500MPa. Initially, we calculate the upper limit of H2 content of sI hydrates by studying the hypothetical sI hydrate, where H2 is the single guest component. It is found that the storage capacity of the hypothetical pure H2 sI hydrate could reach 3.5 wt% at 500MPa and 274K. Depending on pressure, the large cavities of the pure H2 hydrate can accommodate up to three H2 molecules while the small ones are singly occupied at most, even at pressures as high as 500MPa, without any double occupancy being observed. Subsequently, the binary H2-ethylene oxide (EO) hydrate is examined. In this case, the large cavities are occupied by a single EO molecule while the small cavities can accommodate at most a single H2 molecule. Such configuration results in a maximum H2 content of only 0.37wt%. The hydrogen storage capacity does not improve significantly even in case when EO is replaced by a component with smaller molecular weight.