The role of lithium in hydrogen storage in aromatic carbon materials

Three representative aromatic carbon compounds, C6H6, C10H8 and C13H9, are chosen to simulate H2 adsorptions in aromatic carbon materials. The calculations of H2 locating on top of the hexagon center, middle of C–C bond and a C atom of these compounds using density functional and the second order Møller–Plesset perturbation theories indicate that the bindings of H2 with these compounds are very weak. However, the binding is significantly enhanced when lithium is introduced between the H2 and the aromatic carbon compound. In particular, the binding energy of H2 at Li adsorbed on top of the C13H9 is as large as 2.5 kcal mol−1, one order of magnitude enhanced. Such a stable H2 adsorption and the moderate adsorption energy facilitate good H2 storage. According to the similarity of surface features and chemical reactivities among the various aromatic carbon compounds and carbon nanotubes, we conjecture that the H2 storage in these materials would all be enhanced by introducing Li.