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.