The hydrogen storage behavior of Li-decorated monolayer WS2: A first-principles study

Abstract

The hydrogen storage properties of Li-decorated graphene-like monolayer WS2 have been systematically studied by using first principles calculations based on density functional theory. The present results bring to light that the pristine WS2 is not suitable for storing hydrogen due to the very weak interaction between the pristine WS2 sheet and the H2 molecules. The Li atoms can be adsorbed strongly on both sides of WS2 without clustering owing to the larger binding energy of Li to WS2 sheet and the Coulomb repulsion between the Li adatoms. The results reveal that the adsorption of H2 molecules comes from not only electrostatic force between the Li atom and H2 molecules, but also the hybridization mechanism between the σ orbital of H2 molecules and the p orbital of S atom. This is quite different from the other materials where there are no orbital hybridizations between the H2 molecules and the host materials. For the 2Li/WS2 system, the average adsorption energy is 0.13 eV/H2, indicating that Li decorated WS2 can be an optimal choice for the reversible hydrogen adsorption/desorption at room temperature.