Theoretical insights on the influence of doped Ni in the early stage of graphene growth duringthe CH4 dissociation on Ni-Cu(111) surface

CH4 dissociation on the Ni doped Cu(111) surface has been studied theoretically. Our results show that the doped Ni not only maintains its own activity, but also improves the activity of neighbouring surface Cu atoms during CH4 dissociation. The microkinetic analysis demonstrate that the coverage of CH3 becomes higher than that of CH on surface Ni when H-2/CH4 ratio is larger than 1, while the coverage of CH3 on Cu atom is nearly the same when H-2 is introduced. With the increase of temperature, the branching rate of Ni increases, while that of Cu decreases. Compared with temperature, opposite behavior is found with the increase of H-2/CH4 ratios. Furthermore, the behavior of C atom on Ni Cu(111) is discussed. The doped Ni has little influence for C migration, while it depresses the polymerization process on the neighbouring Cu atoms. Free C atoms produced by CH4 dissociation prefer to dissolve on the site having subsurface Ni atom. Once within the bulk, the C atom will move toward the site where surface Ni exists. Then it will dissolve out to contribute the formation of graphene. (C) 2015 Elsevier B.V. All rights reserved