Electronic Structure Calculations of Hydrogen Storage in Lithium Decorated Metal-Graphyne Framework

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-Li-8 by Dewar coordination. On saturation with hydrogen, each Li atom physisorbs three H-2 molecules resulting in MGF-Li-8-H-24.H-2 and Li interact by charge polarization mechanism leading to elongation in average H- H bond length indicating physisorption. Sorption energy decreases gradually from to 0.20 eV on H-2 loading. Molecular dynamics simulations and computed sorption energy range indicate the high reversibility of H-2 in the MGF-Li-8 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.