BeS decorated with alkali-metal atom for outstanding and reversible hydrogen storage: A DFT study

The potential for decorating single Li, Na, or K atoms onto BeS monolayers and their subsequent hydrogen storage performance were investigated using first-principle density functional theory (DFT) calculations. The single-atom Li, Na, or K exhibited strong adhesion to the BeS monolayer, with binding energies of -2.662 eV, -1.982 eV, or -1.669 eV, respectively. Each Li or Na atom on BeS demonstrated the ability to capture four H2 molecules, while a single K atom could bind only three H2 molecules. Notably, Li exhibited stronger binding with stored H2 compared to Na or K. Moreover, by increasing the number of Li atoms on each side of the BeS monolayer to nine, the storage of H2 molecules was improved to a total of 54, concomitant with an advantageous average adsorption energy of -0.236 eV. This enhancement resulted in a significant increase in the hydrogen storage capacity to 6.514 wt%. Molecular dynamics simulations indicated a desorption temperature of approximately 450 K, with the 18 Li atoms remaining strongly bonded to the BeS due to their high diffusion energy of 0.578 eV. Thus, the Li-decorated BeS monolayer emerges as a promising substrate for achieving exceptional and reversible hydrogen storage performance.