Supercritical adsorption in nanoporous materials

The excess adsorbed density ( ex) is defined as the difference between the total amount of adsorbate molecules (N ) found within the volume Vvoid of a measurement cell containing the adsorbent at a given temperature and pressure, minus the number of molecules Ng that would have been found in the void volume in the absence of adsorbate-adsorbent interactions. The volume Vvoid is the sum of the pore volume of the adsorbent Vp re and the volume of the section of the cell which contains no adsorbent (VEmpty)- The number Ag is 

The excess adsorbed density is obtained by dividing this expression by the mass M of the adsorbent in the cell  

Note that N/M is not equal to the absolute adsorbed density since it also includes molecules in the volume VEmpty In terms of the local density, Eq. 

The number of adsorbate molecules inside TEmpty is Pgl Empty and the void volume is Tvoid = Empty + Ipore- Eq. (10.1) can be expressed in terms of the absolute adsorption by the following equation  

The quantity of hydrogen (in moles) stored in an adsorption-based storage unit of total Volume Vsys can be estimated using the following expression  

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