Glassy materials as a hydrogen storage medium: Density functional calculations

The adsorption of molecular hydrogen on a glassy material and its relatives is studied with a use of pseudopotential density-functional method. The binding energy and distance of adsorbed hydrogen is particularly calculated. It is found that the desorption temperature of hydrogen in layered boron oxide is significantly higher than that in carbon nanotubes as much as twice, which is attributed to heteropolar bonding in boron oxide. The effect of water addition to boron oxide on hydrogen adsorption is also investigated. Our results indicate that water may reduce the surface area of boron oxide but has little effect on the hydrogen adsorption energy. We also calculated an optimum pore size for hydrogen diffusion into boron oxide. The current study demonstrates a pathway to the finding of a class of materials for hydrogen storage media that can hold hydrogen at ambient conditions through physisorption.