Truncated pore network model for the methane and hydrogen adsorption in disordered nanoporous carbons

A useful computational model is described for representing the nanoporous structure in real carbons. The model gathers geometric and topological (e.g. pore connectivity and deadend pores) characteristics and it is used to evaluate the effect that porosity (ɛ) and pore size (H) have on the adsorption behavior of methane and hydrogen (obtained by Grand Canonical Monte Carlo Simulation) quantified in terms of the excess density (ρ) and the gravimetric storage capacity (wt.%). In general higher adsorptions are observed compared to the traditional pore models. An increase in porosity or pore size originates a decrease in ρ. 3.1 wt.% is the maximum amount of H2 stored in the material ε=0.40,H=4.89σffε=0.40,H=4.89σff at 77 K, which is in reasonably good agreement with experimental data. This quantity is lower as the porosity decreases and the pore size increases. The results of this work support some experimental evidences that suggest a linear relation between the hydrogen stored in nanoporous carbons and specific surface area.

Research highlights► The model describes more appropriately the different structures present in real carbons. ► Omission of topological properties leads to an underestimation of the isotherms. ► The adsorbed H2 amount in the simulation is proportional to the surface area. ► The model let to study how the structure affects the storage capacity.