Capability of Gas Hydrates as Hydrogen Storage Medium

Abstract

Gas hydrates allow for compact storage of various gases in the hydrate-cages composed of water molecules. The storage and transport systems of natural gas or hydrogen, which take advantage of the characteristics of gas hydrates, have been a focus of constant attention as new techniques. The formation of hydrogen hydrate, however, requires severe conditions of high pressures over 100 MPa or extremely low temperatures. The addition of another guest species has been thought to be most likely way to overcome severe conditions, while it decreases the storage density of hydrogen. In this review, the thermodynamic stabilities of mixed gas hydrates and the hydrate-cage occupancies of hydrogen and additional guest species are described. From the viewpoints of the formation condition and storage density for the mixed gas hydrate, the capability of gas hydrates as hydrogen storage medium is briefly discussed.