Hydrogen storage properties of C₆S₆Li₆: A density functional theory study

In this paper, the hydrogen storage properties of C₆S₆Li₆ were studied by two density functional methods. C₆S₆Li₆ was dynamically stable and could adsorb up to 38 H₂ molecules with a hydrogen storage density of 20.213%. The average adsorption energy of C₆S₆Li₆(H₂)₃₈ was very close to the energy range (0.1-⁃0.8 eV) for reversible hydro-⁃ gen storage at near ambient conditions. Various wave function analysis methods revealed that the 2s→2p electron transition of Li in C₆S₆Li₆ and the electric field of each charged atom jointly dominated Van der Waals attractions between C₆S₆Li₆ and hydrogen molecules. Thermo-⁃chemistry calculations indicated that 6, 32, and 38 H₂ molecules in C₆S₆Li₆(H₂)₃₈ could be readily adsorbed at 77 K and desorbed at 298.15 K under 0.1, 2.5, and 5.0 MPa, respectively. This process corresponds to the reversible hydrogen storage densities of 3.846%, 17.582%, and 20.213%. Atom den-⁃ sity matrix propagation (ADMP) molecular dynamic simulations indicated that most of the hydrogen molecules in C₆S₆Li₆(H₂)₃₈ got efficiently released at room temperature. The (C₆S₆Li₆)₂ dimer could also adsorb 53 H₂ molecules with a gravimetric density of 15.014%. The average adsorption energy for C₁₂S₁₂Li₁₂(H₂)₅₃ could approach the revers-⁃ ible energy range for hydrogen storage.