Ice XVII as a Novel Material for Hydrogen Storage

Hydrogen storage is one of the most addressed issues in the green-economy field. The latest-discovered form of ice (XVII), obtained by application of an annealing treatment to a H2 -filled ice sample in the C0-phase, could be inserted in the energy-storage context due to its surprising capacity of hydrogen physisorption, when exposed to even modest pressure (few mbars at temperature below 40 K), and desorption, when a thermal treatment is applied. In this work, we investigate quantitatively the adsorption properties of this simple material by means of spectroscopic and volumetric data, deriving its gravimetric and volumetric capacities as a function of the thermodynamic parameters, and calculating the usable capacity in isothermal conditions. The comparison of ice XVII with materials with a similar mechanism of hydrogen adsorption like metal-organic frameworks shows interesting performances of ice XVII in terms of hydrogen content, operating temperature and kinetics of adsorption-desorption. Any application of this material to realistic hydrogen tanks should take into account the thermodynamic limit of metastability of ice XVII, i.e., temperatures below about 130 K.