Theoretical study of H₂ adsorption on LiF molecule under an external electric field

The adsorption properties of H₂ on LiF molecule under an external electric field are studied by using DFT method. The results show that H₂ can form weak physical adsorption on the Li or F atom. However, the external electric field can enhance the adsorption energy of single H₂ on the Li/F from -0.112/-0.122 eV without an electric field to -0.122/-0.171 eV with the field intensity of 0.005 a.u., respectively. It is more stable when H₂ is adsorbed on F atom. The mechanism of electric field enhancing the adsorption of H₂ on LiF is also explored through the quantum theory of atoms in molecules (QTAIM). The results reveal that the electric field not only promotes the charge transfer between LiF and H₂, but also makes LiF and H₂ polarized, and thus improves the adsorption. Under the electric field, the LiF molecule can adsorb ten H₂ molecules at most, and the corresponding mass density of hydrogen storage reaches to 43.5 wt %. Our results suggest that the LiF-based materials adsorbed H2 under an external electric field is a potential method for hydrogen storage. (authors)