To explain the fast kinetics of H in porous carbon, it was proposed that the migration relied upon H hopping from a carbon nanotube to another. Using density functional theory, it was found that the barrier for H hopping became smaller than that for diffusion along a tube for certain carbon nanotube separations, decreasing to less than 0.5eV for separations of ∼3.1Å. Such significant reduction occurred irrespective of radius, chirality, registry, and orientation of the two carbon nanotubes: the diffusion was thus facilitated by the porous nature of the material itself. The mechanism proposed was applicable for any porous carbon-based nanomaterials.

Migration Mechanism for Atomic Hydrogen in Porous Carbon Materials. Narayanan, B., Zhao, Y., Ciobanu, C.V.: Applied Physics Letters, 2012, 100[20], 203901