Lithium and Sodium Decorated Graphdiyne As a Candidate for Hydrogen Storage: First-principles and Grand Canonical Monte Carlo Study

Here through doping Boron element in the aromatic ring of the graphdiyne, we demonstrate that the preferred adsorption site for Li and Na can be changed effectively. For double side Li and Na decorations on the Boron-doped aromatic ring, the binding energies are 2.35 eV and 1.65 eV, which are much larger than their own bulk cohesive energies of1.63 eV and 1.13 eV respectively, indicating that Li and Na atoms will be dispersed evenly on the graphdiyne instead of forming metal clusters. We further investigate H-2 storage by using first-principles method. It is found that the average binding energies for Li- and Na-decorated boron-graphdiyne structure with 5 adsorbed H-2 molecules per metal, are all in the optimum adsorption energy range (0.2-0.4 eV), which are 0.33, 0.31, 0.29, 0.24 and 0.21 eV for Li-decoration and 0.26, 0.26, 0.26, 0.24 and 0.22 for Na-decoration. Moreover, the molecular dynamics calculations demonstrate our structures are thermodynamic stable under realistic experimental condition. The estimated H-2 uptake capacities could reach to 8.81 wt% for Li-decoration and 7.73 wt % for Na-decoration. Finally, we fitted the force field parameters and performed the grand canonical Monte Carlo simulations to address the H-2 uptake capacity.