Atomic Hydrogen Diffusion on Doped and Chemically Modified Graphene

To explore hydrogen mobility on graphene, density functional calculations are used to determine the magnitude of binding energy versus the diffusion barrier for graphene, considering the effects of hole and electron doping, B and N substitutional dopants, and oxygen heteroatoms. Although C-H binding energy and the barrier for chemical diffusion are not correlated, the binding energy of H in the lowest energy site on top of a C atom correlates with the binding energy of H over a "bridge" C-C bond, which is the transition state for chemical diffusion. Using this framework, we demonstrate that both B substitutionally doped graphene and hydoxylated graphene have the potential to simultaneously meet thermodynamic and kinetic constraints for reversible room-temperature hydrogenation. The constraints demonstrate that reversible room-temperature hydrogenation is possible only when H diffuses in a chemically bound state.