Molecular Dynamics Insight into the Dissociation Kinetics of Hydrogen Hydrate Protected by Ice Shell

Abstract

Hydrogen hydrates are promising for hydrogen storage owing to high capacity and safety, yet the poor stability hinders its practical applications. This study used molecular dynamics simulations to systematically explore the stabilizing effect of an Ice Ih shell on hydrogen hydrates. At 260 K and 10 MPa, the quasi-liquid layer caused by the dissociation of hydrates retarded the diffusion of hydrogen from the hydrate to the gas phase but cannot prevent complete decomposition. In systems with an Ice Ih shell, structural transformation at the ice–hydrate interface dominates stability, strongly dependent on cage occupancy. Low-occupancy hydrates remain stable under superheating conditions, whereas high-occupancy ones fully dissociate as the ice shell converts to hydrate, thins, and collapses. This work clarifies the molecular stabilization mechanism of ice shell-protected hydrogen hydrates, offering a theoretical foundation for stable hydrogen storage and transportation via hydrate-based technologies.