Abstract:
Porous metal−graphyne framework (MGF) made up of graphyne
linker decorated with lithium has been investigated for hydrogen storage. Applying
density functional theory spin-polarized generalized gradient approximation with the
Perdew−Burke−Ernzerhof functional containing Grimme’s diffusion parameter with
double numeric polarization basis set, the structural stability, and physicochemical
properties have been analyzed. Each linker binds two Li atoms over the surface of the
graphyne linker forming MGF-Li8 by Dewar coordination. On saturation with
hydrogen, each Li atom physisorbs three H2 molecules resulting in MGF-Li8-H24. H2
and Li interact by charge polarization mechanism leading to elongation in average H−
H bond length indicating physisorption. Sorption energy decreases gradually from
≈0.4 to 0.20 eV on H2 loading. Molecular dynamics simulations and computed
sorption energy range indicate the high reversibility of H2 in the MGF-Li8 framework
with the hydrogen storage capacity of 6.4 wt %. The calculated thermodynamic
practical hydrogen storage at room temperature makes the Li-decorated MGF system
a promising hydrogen storage material.
