The thermodynamic, kinetic and magnetic properties of the hydrogen monomer on doped graphene layers were studied by ab initio simulations. Electron doping was found to heighten the diffusion potential barrier, while hole doping lowers it. However, both kinds of dopings heighten the desorption potential barrier.The underlying mechanism was revealed by investigating the effect of doping on the bond strength of graphene and on the electron transfer and the coulomb interaction between the hydrogen monomer and graphene. The kinetic properties of H and D monomers on doped graphene layers during both the annealing process (annealing time t 0 =300 s) and the constant-rate heating process (heating rate α =1.0 K/s) were simulated. Both electron and hole dopings were found to generally increase the desorption temperatures of hydrogen monomers. Electron doping was found to prevent the diffusion of hydrogen monomers, while the hole doping enhances their diffusion. Macroscopic diffusion of hydrogen monomers on graphene can be achieved when the doping-hole density reaches 5.0 × 10 13 cm −2 . The magnetic moment and exchange splitting were found to be reduced by both electron and hole dopings, which was explained by a simple exchange model. The study in this report can further enhance the understanding of the interaction between hydrogen and graphene and is expected to be helpful in the design of hydrogenated-graphene-based devices.

The understanding of the kinetic properties of hydrogen (isotopes) adatoms on graphene is important in many fields. The kinetic properties of hydrogen-isotope (H, D, and T) monomers were simulated using a composite method consisting of density functional theory, density functional perturbation theory, and harmonic transition state theory. The kinetic changes of the magnetic property and the aromatic π bond of the hydrogenated graphene during the desorption and diffusion of the hydrogen monomer were discussed. The vibrational zero-point energy corrections in the activation energies were found to be significant ranging from 0.072 to 0.205 eV. The results obtained from quantum mechanically modified harmonic transition state theory were compared with the ones obtained from classical-limit harmonic transition state theory over a wide temperature range. The phonon spectra of hydrogenated graphene were used to closely explain the (reversed) isotope effects in the prefactor, the activation energy, and the jump frequency of the hydrogen monomer. The kinetic properties of the hydrogen-isotope monomers were simulated under conditions of annealing for 10 min and of heating at a constant rate (1.0 K/s). The isotope effect was observed; that is, a hydrogen monomer of lower mass is desorbed and diffuses more easily (with lower activation energies). The results presented herein are very similar to other reported experimental observations. This study of the kinetic properties of the hydrogen monomer and many other involved implicit mechanisms provides a better understanding of the interaction between hydrogen and graphene.

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