DOD–Graphene: A Promising sp ² -Carbon Monolayer for Hydrogen Storage

We report a first-principles study of a novel two-dimensional carbon allotrope, termed Dewar-Octa-Decagraphene (DOD-graphene), and evaluate its potential as a solid-state hydrogen carrier upon lithium functionalization. The pristine monolayer is metallic and dynamically stable. It remains intact during ab initio molecular dynamics (AIMD) at 300 K. Single-atom adsorption shows that Li binds strongly at the centers of the decagonal pores (-2.97 eV) and donates ∼0.8 e to the π network. A fully saturated configuration with two Li per decagon preserves metallicity and withstands AIMD at room temperature. Successive adsorption of up to 20 H₂ molecules (7.52 wt %) yields average binding energies ranging from -0.30 to -0.20 eV, which are optimal for reversible storage without dissociation. Thermodynamic isotherms predict full capacity at 300 K under ∼10 atm. At the same time, AIMD simulations confirm rapid desorption: most H₂ molecules leave the surface within 3 ps at 300 K without compromising structural integrity. Projected density of states, charge-density difference, and reduced density gradient analyses reveal negligible charge transfer to H₂ and identify van der Waals interactions mediated by Li⁺ centers. The combination of robust Li anchoring, high gravimetric capacity, and facile, physisorptive release positions Li-decorated DOD-graphene as a promising candidate for next-generation hydrogen storage media.