Lithium-decorated SiB monolayer for reversible hydrogen storage: High-capacity realization through strain engineering

The feasibility of using a Li-decorated SiB monolayer for hydrogen (H2) storage was evaluated via first-principles calculations. The results showed that a single Li atom anchored on the SiB monolayer can adsorb up to three H2 molecules with a physical adsorption energy of-0.18 eV/H2. However, each Li atom on the saturated structure (Li12Si12B12 monolayer) can only adsorb two H2 molecules due to the narrow space between Li atoms, yielding 8.1 wt% of H2 gravimetric density. The reversible binding to H2 molecules can be achieved in the temperature range of 100-300 K; H2 molecules attached on the Li12Si12B12 monolayer were allowed to be released in large quantities at 300 K. Considering the excellent structural stability of SiB monolayer under mechanical strain, biaxial tensile strain was applied to the Li-decorated SiB monolayer to address the problem of insufficient storage space for hydrogen. Excitingly, the H2 gravimetric density on the Li12Si12B12 monolayer under 7 % biaxial tensile strain was raised up 10.8 wt% (33 % higher than the unstrained system). These results reveal a broad-prospect of Li-decorated SiB monolayer for reversible hydrogen storage application, and also suggest new insights into enhancing the hydrogen storage capacity under a variable biaxial tensile strain.