Hydrogen storage capacities of nanoporous carbon calculated by density functional and Møller-Plesset methods

The hydrogen storage capacities of nanoporous carbons, simulated as flat graphene slit pores, have been calculated using a quantum-thermodynamical model. The model is applied for several interaction potentials between the hydrogen molecules and the graphitic walls that have been generated from density functional theory (DFT) and second-order M{}ller-Plesset (MP2) calculations. The hydrogen storage properties of the pores can be correlated with the features of the potential. It is shown that the storage capacity increases with the depth of the potential, Dₑ. Moreover, the optimal pore widths, yielding the maximum hydrogen storage capacities, are close to twice the equilibrium distance of the hydrogen molecule to one graphene layer. The experimental hydrogen storage capacities of several nanoporous carbons such as activated carbons (ACs) and carbide-derived carbons (CDCs) are well reproduced within the slit pore model considering pore widths of about 4.9--5.1 for the DFT potential and slightly larger pore widths (5.3--5.9 ) for the MP2 potentials. The calculations predict that nanoporous carbons made of slit pores with average widths of 5.8--6.5 would yield the highest hydrogen storage capacities at 300 K and 10 MPa.