Arc plasma-assisted hydrogenation of few-layer graphene in methane-hydrogen atmospheres

Aiming towards high-efficiency hydrogen storage, pristine graphene is usually modified with atomic hydrogen by chemical or physical methods. However, the synthetic procedures of both methods are usually complex and requires specialized equipment. Here, a facile way to produce highly hydrogenated graphene (HG) via DC arc discharge plasma in methane-hydrogen atmosphere is reported. In addition, comparative experiments were also carried out in pure methane and methane-helium systems to probe the effects of chemical nature of buffer gases on the formation of arc nanocarbons. Our studies demonstrate that hydrogen not only leads to a planar growth of carbon radicals, but also plays a crucial role in the conversion from sp(2)- to sp(3)-carbon configuration of graphene lattice in methane-mixed gas discharge. While the addition of helium only facilitates the pyrolysis process of methane and enhances the evaporation efficiency of arc plasma. Based on the experimental results, the growth mechanism of HG in methane-hydrogen arc plasma has been discussed rationally in terms of hydrogen plasma and methane pyrolysis.