Abstract

We have demonstrated that doping alkali cations in charged state can improve the hydrogen adsorption significantly in the molecular form. In addition, the number of hydrogen molecules adsorbed by Li cation doped benzene system was 3 while Na and K doped benzene were able to adsorb up to 6 hydrogen molecules. In general the adsorption energies of alkali atoms and the binding energy/H2 for hydrogen are underestimated by the hybrid B3LYP functional, while MP2 functional provides higher binding energy. The nature of interaction between hydrogen and the alkali center was mainly due to be dipole – quardupole and dipole – induced dipole electrostatic interaction. Further, we extended the present single benzene system to the curved calixarene system. The calixarene ring was able to adsorb up to five alkali atoms, one inside the cavity and 4 on the walls of the cavity and this system was capable to adsorb up to 30 H2 molecules in molecular form at low temperature.