Boron-tuned bonding mechanism of Li-graphene complex for reversible hydrogen storage

Based on first-principles density functional theory, we show that boron-doping significantly enhances the Li bond strength on the graphene. The transition from s-p hybridization of the Li-graphene complex to p-p hybridization of the Li-coated boron-doped graphene is responsible for the enhanced binding energy. The charge redistribution induced by boron-doping gives rise to two parts of an electrostatic potential energy (one is around the Li atom and the other is parallel to the graphene plane). Four polarized H-2 molecules are attached to one Li atom with an optimal binding energy of similar to 0.13 eV/H-2.