Hydrogen diffusion in C-1' phase clathrate hydrate

Recently, a new phase C-1' H2 hydrate was experimentally identified. In this work, the diffusive behaviors of H-2 in C-1' phase clathrate hydrate are explored using classic molecular dynamics (MD) simulations. It reveals that the cage occupancy by H-2 molecule negligibly influences the C-1' phase clathrate structure but greatly dictates the diffusion coefficient of H(2 )molecule. Due to the small cage size and small windows connecting the neighboring cages in C-1' phase clathrate, non-occupancy of the neighboring cages is demanded to enable the diffusion of H-2 molecule that is primarily dominated by hopping mechanism. Moreover, the analysis of diffusive free energy landscape reveals lower energy barrier of H-2 molecule in C-1' phase clathrate hydrate than that of other gases in conventional clathrate hydrates, and that H-2 molecule travels through the windows between neighboring cages with preferential molecular orientation. This study provides critical physical insights into the diffusion behaviors of H-2 in the C-1' phase clathrate hydrate, and implies that the C-1' clathrate hydrate is a promising solid structure for the next-generation H-2 storage.