Mechanism of heterogeneous adsorption in the storage of hydrogen in carbon fibers activated with supercritical water and steam

In the present work we study the capacity of storage hydrogen on carbon fibers activated with supercritical water and with steam on the basis of a multisite Langmuir model, with three energetically different adsorption sites that may be associated with pores of different sizes: i) very small micropores, accessible only to hydrogen; ii) micropores detected by the adsorption of CO2, and iii) micropores detected by the adsorption of N2. The correlation of the experimental data with the model allowed the amount of hydrogen stored in each of the sites to be quantified and confirmed that hydrogen storage mechanism begins with the filling of the smallest pores. Additionally, from the model it was possible to interpret the dependence of the amount of hydrogen stored with textural parameters such as the micropore volumes. The model also allowed the storage capacity of the fibers to be predicted for pressures higher than those obtained experimentally.