The role of lithium in hydrogen storage in aromatic carbon

Three representative aromatic carbon compounds, C6H6, C10H8 and C13H9, are chosen to simulate H-2 adsorptions in aromatic carbon materials. The calculations of H-2 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 Moller-Plesset perturbation theories indicate that the bindings of H-2 with these compounds are very weak. However, the binding is significantly enhanced when lithium is introduced between the H-2 and the aromatic carbon compound. In particular, the binding energy of H-2 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 H-2 adsorption and the moderate adsorption energy facilitate good H-2 storage. According to the similarity of surface features and chemical reactivities among the various aromatic carbon compounds and carbon nanotubes, we conjecture that the H-2 storage in these materials would all be enhanced by introducing Li. (C) 2004 Elsevier B.V. All rights reserved.