Multiscale Investigation of Hydrogen Adsorption in Vacancy-Engineered CNCs: A Combined DFT and PHITS Monte Carlo Study

The rapid exhaustion of fossil fuel resources, coupled with increasing environmental degradation, has driven the pursuit of sustainable and clean energy carriers. Hydrogen, in particular, has attracted considerable attention as a potential alternative energy medium capable of addressing these challenges, while also aligning with the performance targets established by DOE. This study systematically investigates the synergistic effects of mono-vacancy engineering (V1 at the apex, V2 away from the apex) on the hydrogen adsorption properties of carbon nanocones (CNCs) across five disclination angles (60˚ - 300˚). First-principles DFT calculations (B3LYP/6-31G) reveal that the C89H10-V1-HS2 configuration at a 300˚ disclination angle possesses the most favorable adsorption energy of −4.95 eV, a peak dipole moment of 24.21 D, and a minimum energy gap of 0.02 eV. Complementary Monte Carlo simulations performed via PHITS 3.35 provide a macroscopic validation, demonstrating that these vacancy sites act as focal points for energy localization. The results indicate a maximum localized temperature rise of 34.8 K and an absorbed dose of 0.82 Gy. These findings confirm that vacancy-induced electronic modulation, combined with localized thermal excitation, significantly enhances the hydrogen storage potential of CNCs for irradiation-assisted applications.