First-principl Study For Hydrogen Storage On Graphene

Hydrogen is a highly ideal energy carrier due to its abundance and environmental friendli-ness. Recently, special attention has been attracted to nanostructured materials because of their potentially high gravimetric hydrogen capacity, safety, and high efficiency of filling and deliver-ing. Many new theoretical designs and experimental methods for construction of high capacity ambient temperature reversible hydrogen adsorption materials have been explored using metal atoms doped on carbon nanomaterialsFirstly, we explored the method with the ethylene molecules and Ti, Li atoms intercalated into the graphite to open space for the physisorption of hydrogen based on first-principle plane-wave calculations. Our simulation indicated that the interlayer distance of the graphene is close to the optimal physisorption of hydrogen with this method.Secondly, we proposed a system that has the potential to be a good candidate for hydrogen storage, in which multiple hydrogen molecules can be adsorbed in the ground state around an impurity in graphene at a certain optimal ILD (interlayer distance). Our first-principle calcu-lations predict that this complex, Ti atoms embedded in double-vacancy graphene (Ti@DV), can hold up to eight H2per unit. The hydrogen molecules are not dissociated and are all stored in molecular form, so adsorption and desorption of hydrogen should be feasible. Furthermore, this type of structure is stable throughout the charging and discharging process. The density of states (DOS) of this hydrogen storage medium indicates little charge transfer between H2and Ti@DV graphene.The third, an investigation on the hydrogen molecule adsorption on the graphdiyne has been made. Graphdiyne is a promising candidate for hydrogen storage due to its larger surface area compared to graphene. The results show that the Ti or Li atom can be absorbed on the hollow site of graphdiyne and there are four hydrogen molecules per metal atom. In the last, inspired by the method from the field of DNA and protein, a brief discussion about the van der Waals forces correction to the density functional theory was made. Our results show that this method may give a more precise description of the carbon-based nanomaterials for hydrogen storage.