Fig 8. Relaxed structures of the H2molecule adsorbed onto a) Li decorated SV silicene and b) Li decorated SW silicene.
The H2 adsorption energy in each system was calculated using Equation (3) and was negative in all instances thus indicating that hydrogen adsorption is favourable on these substrates. While pristine silicene shows a H2 adsorption energy of -0.12 eV/H2 which is much higher than pristine graphene with their relaxed structures available in Fig. S4, the presence of lithium and defects greatly improved the hydrogen binding energies showing binding energies of -0.242 eV/H2 and -0.261 eV/H2 for the SV silicene and SW silicene respectively. Both the lithium decorated defective systems show H2adsorption energies which are higher than pristine silicene and well within the DOE range with the SW silicene system showing slightly higher adsorption energies compared to the SV silicene system. The shorter distance between the Li atom and H2 in the SW silicene system compared to SV silicene further supports the higher H2 binding energies present in the Stone-Wales system. A detailed summary of the H2 adsorption results can be seen in Table 2.