Pressure-Induced Enhancement of Hydrogen Storage in 3D Honeycomb Carbon Network: Insights from DFT and Molecular Dynamics Simulations

Using dispersion-corrected density functional theory, we examine the pressure-induced changes in molecular hydrogen adsorption within an undecorated three-dimensional honeycomb carbon framework. At ambient pressure, hydrogen binding is too weak to support practical storage applications. With increasing pressure, the honeycomb framework retains its structural integrity while exhibiting significant electronic-structure modifications, including charge redistribution within C–C bonds that enhances van der Waals interactions and strengthens hydrogen binding. The adsorption energy reaches –0.23 eV, satisfying the U.S. Department of Energy (DoE) criteria for hydrogen storage at high pressure. Further adsorption of H2 molecules leads to an increase in the magnitude of adsorption energy due to enhanced local polarization effects. The honeycomb structure can accommodate 47 H2 molecules, yielding a gravimetric capacity of 6.58 wt % at 5 GPa pressure. The results of hydrogen desorption confirm the feasibility of storage near room temperature. Hydrogen desorption analysis indicates storage feasibility near room temperature, while ab initio molecular dynamics simulations confirm the thermodynamic stability of the structure under elevated pressure and ambient temperature. These findings highlight honeycomb carbon as a promising candidate for efficient hydrogen storage under high-pressure conditions.