A computational study on hydrogen storage in potential wells using K-intercalated graphite oxide

Abstract

Using ab initio electronic structure calculations and grand canonical Monte Carlo simulations, we investigate the storage capacity of hydrogen molecules in a potential well created inside potassium-intercalated graphite oxide layers. We show that the binding energy of hydrogen located between layers of graphite oxide mainly originates from the dispersion interaction, and it is further increased slightly by induced dipole interactions. Its strength is fairly insensitive to the precise positions of the hydrogen molecules on the graphene plane, so the system may be described as a quasi-two-dimensional potential well. In this situation, the storage capacity is enhanced by the corresponding Boltzmann factor based on equilibrium thermodynamics. The trend of storage capacity with different geometries and chemical compositions of the scaffold materials is explained. With the present model, the density functional theory calculations and grand canonical Monte Carlo simulations predict a 2.5 wt% hydrogen storage capacity at room temperature at 10 MPa. For a model with increased potential depth, the storage capacity is predicted to increase up to 5.5 wt%.