Li adsorption on monolayer and bilayer MoS_2 as an ideal substrate for hydrogen storage

Based on the first-principles plane wave calculations, we show that Li adsorbed on monolayer and bilayer MoS2 forming a uniform and stable coverage can serve as a high-capacity hydrogen storage medium, and Li-coated MoS2 can be recycled by operations at room temperature due to Li having strength binding, big separation and is stable against clustering. The full Li coverage MoS2 system（2 ＊ 2 hexagonal MoS2 supercell） can reach up to eight H2 molecules on every side, corresponding to the gravimetric density of hydrogen storage up to 4.8 wt% and 2.5 wt% in monolayer and bilayer MoS2, respectively. The adsorption energies of hydrogen molecules are in the range of 0.10 e V/H2–0.25 e V/H2,which are acceptable for reversible H2 adsorption/desorption near ambient temperature. In addition, compared with light metals decorated low dimension carbon-based materials, the sandwiched structure of MoS2 exhibits the greatly enhanced binding stability of Li atoms as well as slightly decreased Li-Li interaction and thus avoids the problem of metal clustering.It is interesting to note that the Li atom apart from the electrostatic interaction, acts as a bridge of hybridization between the S atoms of MoS2 and adsorbed H2 molecules. The encouraging results show that such light metals decorated with MoS2 have great potential in developing high performance hydrogen storage materials.