First-principles design of Na-decorated β-TPDH for lightweight hydrogen storage

First-principles calculations reveal that Na-decorated β-TPDH is a highly promising carbon-based monolayer for reversible hydrogen storage. Sodium atoms adhere strongly to the β-TPDH surface, maintaining the underlying framework while inducing charge transfer that strengthens H₂ adsorption. The optimized Na@β-TPDH complex can host up to 10 H₂ molecules—equivalent to five H₂ molecules per Na atom—achieving a gravimetric storage capacity of 9.59 wt% with an average adsorption energy of −0.163 eV per H₂. This storage capacity significantly surpasses the U.S. Department of Energy (DOE) benchmark of 6.5 wt%, and the adsorption energy lies within the optimal window for reversible hydrogen uptake and release. Bader charge analysis, charge density difference (CDD), and projected density of states (PDOS) calculations demonstrate that H₂ binding is predominantly governed by Na-induced charge polarization, complemented by weak van der Waals interactions, and occurs without dissociation of the H₂ molecules. The estimated desorption temperature is 208.80 K at 1 atm, pointing to moderate release conditions. Phonon dispersion, elastic constant analyses, and ab initio molecular dynamics (AIMD) simulations confirm that the proposed material is dynamically, mechanically, and thermally stable. AIMD simulations of the fully hydrogen-loaded structure further corroborate the reversibility of H₂ adsorption and desorption. Collectively, these findings position Na@β-TPDH as a strong lightweight contender for solid-state hydrogen storage applications.