  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 $\alpha =$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
$5.0\times10^{13}$ 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.
