Theoretical Insights on the C2Hy Formation Mechanism During CH4 Dissociation on Cu(100) Surface

The possible C2Hy (y = 2-6) formation reactions (CHx + CHz -> C2Hy (y = x + z)) and activated second-order CHx+1 + CHz-1 reactions (CHx + CHz -> CHx+1 + CHz-1) during CH4 dissociation on Cu(100) surface have been investigated by using the density functional theory. Our results show that C2Hy (y = 2, 4) formation reactions are favorable both kinetically and thermodynamically, compared with the direct dehydrogenation of CH4 (CHx -> CHx-1 + H) and second-order CHx+1 + CHz-1 reactions. The second-order CHx+1 + CHz-1 reactions are less competitive compared with the direct dehydrogenation of CHx Both DFT calculations and microldnetic model demonstrate that the reaction CH + CH -> C2H2 is a major channel to produce C2H7 at a temperature of 860 degrees C, followed by CH3 + CH -> C2H4. When the H-2 influence is introduced, the major intermediate changes from CH to CH3 on Cu(100) surface with the increase of H-2 partial pressure, while the coverage difference between CH and CH3 is not significant. This means that both species will have a large influence on the graphene growth mechanism.