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 H2 molecules are attached to one Li atom with an optimal binding energy of ∼0.13 eV/H2.