▎ 摘　　要

In this work, we performed QM/MD simulations to investigate the hydrogenation process on quasi-free-standing graphene. We found that, at a lower hydrogen incident energy of 0.4 eV, chemisorption occurred in principle in random positions on the graphene surface with little preference for the adsorption site, causing H-frustrated adsorption patterns over time. However, during prolonged exposure to hydrogen, a para-adsorption pattern emerged, producing 25% maximum coverage. In contrast, at higher incident energies of 1.0 and 1.5 eV, the H-frustration pattern emerged at all times, and a higher hydrogen maximum coverage of similar to 50% or 60% was reached. This is because the higher incident energies of 1.0 and 1.5 eV can overcome the barrier of 0.63 eV for continuing hydrogen chemisorption on the C4H structure. Based on potential energy curves for C4H-H with H, hydrogenation on para neighbors is a barrierless reaction, favoring the formation of armchair-like C2H structures. The isotope deuterium increased the coverage compared with hydrogen at the same incident energy. Furthermore, the magnetic properties of various hydrogen clusters observed in our QM/MD simulations were studied. The current results show that C4H and graphene hydrogenated with even numbers of H atoms are nonmagnetic, whereas graphene with odd numbers of hydrogen atoms have one to three unpaired electrons, showing magnetism. Hydrogenation opened the band gap by 0.3-4.0 eV at various chemisorption patterns.