Abstract
Graphene, defected graphene, and lithium-decorated nitrogen-doped graphene are investigated as potential hydrogen storage materials using first-principles density functional theory (DFT) calculations. To prevent metal-metal clustering and maintain stable configurations, Li atoms are strategically positioned within hexagonal carbon rings, enhancing the efficiency of hydrogen adsorption. The results indicate that Li-decoration enables graphene to adsorb three to five hydrogen molecules, achieving a gravimetric hydrogen storage capacity of up to 8.8 wt.%, surpassing the U.S. Department of Energy's recommended target. Among the systems studied, nitrogen doping combined with lithium decoration results in the highest adsorption energy of 0.26 eV per hydrogen molecule, attributed to enhanced charge redistribution. The adsorption energy range supports efficient and reversible hydrogen storage. These findings highlight the potential for defect engineering, doping, and decoration in the tailoring of graphene-based materials for hydrogen storage, which contributes to advances in sustainable energy technologies.