A Step Forward in Understanding the Hydrogen Adsorption and Compression on Activated Carbons
Résumé
Hydrogen adsorption on activated carbons (ACs) is a promising alternative to compression and liquefaction for storing hydrogen. Herein, we have studied hydrogen adsorption on six commercial ACs (CACs) with surface areas ranging from 996 to 2216 m 2 g-1 , in a temperature range of 77 to 273 K and pressures up to 15 MPa. Excess hydrogen adsorption capacities of 2.3 to 5.8 wt. % were obtained at 77 K and 4 MPa. We demonstrated that, contrary to what is normally done, hydrogen capacity is more accurately predicted by the surface area determined by the NLDFT method applied to N 2 and CO 2 adsorption data, than by the BET area. The modified Dubinin-Astakhov (MDA) equation was used to fit the experimental adsorption data, and the relationship between the MDA parameters (n max , V a , α and β) and the textural properties of the CACs was brought for the first time. We concluded that the n max and V a parameters are related to the BET area while the α and β parameters are related to average micropore size and total pore volume, respectively. α and β were used to evaluate the enthalpy and entropy of adsorption and we show that these parameters can be used to assess the best carbon for hydrogen storage or compression.
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