Hydrogen storage in MgH2 coated single walled carbon nanotubes

We present a density functional theory (DFT) study on the hydrogen storage capacity of (5,5) arm-chair single walled carbon nanotubes (SWCNTs) functionalized with magnesium hydride (MgH2). Being lightweight and rich in hydrogen, MgH2 adsorbs H2 molecules in the vicinity of carbon nanotubes. The H2 molecules are adsorbed dissociatively on SWCNT + MgH2 complex. The H–H distance gets increased by more than ten times of the initial bond length 0.74 Å of the H2 molecule. The hydrogen storage capacity of three configurations namely C1MgH2, C5MgH2 and C10MgH2 is reported. The density of states is computed for all the systems. The average binding energies of C5MgH2 and C10MgH2 when H2 molecule is adsorbed are 1.86 eV/H2 and 1.96 eV/H2, which are approximately equal. Thus, increasing the number of MgH2 molecule does not vary the binding energy of H2 adsorption. The corresponding temperature, in which desorption will take place, is 2285 K and 2457 K for C5MgH2 and C10MgH2 systems respectively, which are much above the room temperature.