Studies on the mechanism and capacity of hydrogen uptake by physisorption-based materials

Nanostructure carbons are the most important physisorption-based hydrogen carriers. The mechanism of hydrogen uptake was studied based on the adsorption isotherms collected for a wide range of temperature and pressure. It was concluded that the hydrogen adsorbed is arranged on carbon surface monolayerly; therefore, the storage capacity depends only on the specific surface area of the carbon. This rule applies also for other organic/inorganic materials if the interaction between hydrogen and the solid surface remains the Van der Waals force. Carbon nanotubes cannot be good carriers of hydrogen due to the small surface area, but superactivated carbon is of great potential and a storage capacity over 10 wt% was proven for the condition of 77 K and 6 MPa.