Hydrogen adsorption on nitrogen-doped graphene in the presence of water: An atomistic study

Graphene-based materials are promising candidates for hydrogen storage and filtration owing to their high surface area and tunable surface chemistry. In this study, we investigate the adsorption and diffusion behavior of hydrogen molecules on pristine, nitrogen-doped (graphitic and pyridinic), defective, and functionalized graphene using reactive force field molecular dynamics simulations. The results demonstrate that nitrogen doping significantly strengthens H2–surface interactions, leading to increased hydrogen coordination and suppressed surface diffusion compared to pristine graphene. The influence of water, which is inevitably present under realistic conditions, is also examined and shown to further reduce hydrogen mobility by limiting surface accessibility. In addition, we analyze the effect of oxygen-related surface functionality by introducing OH functional groups, which enhance hydrogen–surface interactions and further suppress hydrogen diffusion. Adsorption energy calculations confirm that both nitrogen dopants and OH functional groups increase the affinity of the graphene surface toward adsorbates, while water molecules bind more strongly than hydrogen, providing a mechanistic explanation for the reduced hydrogen mobility observed under hydrated conditions. This study provides fundamental insights into the effects of both doping and solvation on hydrogen mobility, offering guidance for the rational design of graphene-based materials for efficient hydrogen storage and separation technologies.