High-capacity hydrogen storage in Al-adsorbed graphene

A high-capacity hydrogen storage medium---Al-adsorbed graphene---is proposed based on density-functional theory calculations. We find that a graphene layer with Al adsorbed on both sides can store hydrogen up to 13. 79 wt % with average adsorption energy -0. 193 eV/H₂. Its hydrogen storage capacity is in excess of 6 wt %, surpassing U. S. Department of Energy (DOE's) target. Based on the binding-energy criterion and molecular-dynamics calculations, we find that hydrogen storage can be recycled at near ambient conditions. This high-capacity hydrogen storage is due to the adsorbed Al atoms that act as bridges to link the electron clouds of the H₂ molecules and the graphene layer. As a consequence, a two-layer arrangement of H₂ molecules is formed on each side of the Al-adsorbed graphene layer. The H₂ concentration in the hydrogen storage medium can be measured by the change in the conductivity of the graphene layer.