Harnessing rippled Si9C15 monolayer for efficient hydrogen storage via lithium functionalization: A first-principles study

A recently synthesized rippled Si 9 C 15 monolayer has been reported to possess a direct bandgap (1.82 eV) semiconductor along with thermal and mechanical stability. In this work, first-principles calculations are employed to investigate Li-functionalized Si 9 C 15 (2Li@Si 9 C 15 ) monolayer as a promising platform for reversible hydrogen storage. Lithium adatom binds strongly to the nanosheet with a binding energy of −1.23 eV, ensuring structural integrity up to 500 K. The 2Li@Si 9 C 15 can adsorb multiple H 2 molecules, enabling a maximum uptake of 16H 2 per unit cell with a gravimetric and volumetric storage capacity of 6.68 wt% and 49 g/L surpassing the U.S. Department of Energy 2025 target. The calculated average adsorption energy of −0.20 eV/H 2 places the system as reversible hydrogen storage medium with desorption temperature in the range from 291 to 444K. These findings highlight 2Li@Si 9 C 15 monolayer as a stable, high-capacity, and kinetically favorable hydrogen storage material offering strong potential for next-generation transportation technologies.