Adsorbents storage

The hydrogen storage capacity of sorbent-based systems is in an intermediate level between compressed gas and intermetallic compounds (metal hydrides), involving the transfer of hydrogen molecules to the surface of the pores of solid materials through physical interaction (van der Waals bonding) and the subsequent release of hydrogen, whenever required, by thermal stimulation or other techniques. Different materials have been investigated for their potential use in the storage of hydrogen through adsorption, among them; metal-organic frameworks (MOFs), carbon-based materials, zeolites and polymers of intrinsic microporosity (PIMs) have been some of the most extensively studied due to their fast kinetics, good reversibility and high stability over many cycles. However, due to the weak interactions between hydrogen molecules and the surface of these solid materials, high hydrogen storage capacities are generally achieved at cryogenic temperatures (around -196 °C) and relatively high pressures. At ambient temperature and pressure conditions, hydrogen adsorption capacities are usually very low (<1 wt%.). Some materials, such as MOFs or PIMs, can be designed, assembled and modified on the atomic or molecular levels, and research looks at designing cost-efficient storage solutions with acceptable volumetric and gravimetric densities.