Comparison of DFT characterization methods based on N2, Ar, CO2, and H2 adsorption applied to carbons with various pore size distributions

Adsorption isotherms of N₂, Ar, CO₂, and H₂ were measured on selected activated carbons representing various pore size distributions. Isotherm data were analyzed using the DFT method. A good agreement was obtained between N₂ and Ar results in a wide range of pore sizes. Both N₂ and Ar results agree with CO₂ analysis at 273 K in the range of small micropores where CO₂ analysis is most applicable. Also, in this range of pores the analysis of H₂ adsorption data at 77 K gives results which are consistent with the results obtained from the more conventional vapor-phase adsorptives. However, the range of PSDs calculated from H₂ data extends to pore sizes smaller than those that can be characterized by other adsorbates.