Computational evaluation of Na-decorated C12 monolayer as a reversible hydrogen storage medium

The reversible hydrogen storage performance of two-dimensional TPDH-graphene monolayer decorated with alkali metal Na atoms (Na@C12) was investigated using first-principles calculations. The most stable Na decoration site was firstly identified, with a binding energy of -1.59 eV/atom. A 2 × 1 × 1 C12 monolayer supercell was then constructed fully decorated with four Na atoms at the stable sites. The Na@C12 monolayer demonstrated excellent thermal stability and enhanced electronic properties. It can reversibly adsorbe 16 H2 molecules, achieving a high hydrogen storage capacity of 8.48 wt%. The average adsorption energy ranged from -0.157 to 0.191 eV/H2, corresponding to desorption temperatures of 200-244 K. Furthermore, mechanistic analysis, including partial density of states, charge density difference, and reduced density gradient, revealed that hydrogen adsorption is primarily driven by a combination of orbital interactions, electrostatic forces, and van der Waals interactions. These results indicate that the Na@C12 monolayer is a highly promising material for efficient and reversible hydrogen storage, with strong potential for practical implementation. Additionally, this study broadens the application prospects of 2D C12 materials and offers valuable theoretical guidance for developing next-generation hydrogen storage systems.