Theoretical Insights on the C₂H_y Formation Mechanism During CH₄ Dissociation on Cu(100) Surface

Abstract

The possible C2H y (y = 2–6) formation reactions (CH x + CH z → C2H y (y = x + z)) and activated second-order CH x+1 + CH z–1 reactions (CH x + CH z → CH x+1 + CH z–1) during CH4 dissociation on Cu(100) surface have been investigated by using the density functional theory. Our results show that C2H y (y = 2, 4) formation reactions are favorable both kinetically and thermodynamically, compared with the direct dehydrogenation of CH4 (CH x → CH x–1 + H) and second-order CH x+1 + CH z–1 reactions. The second-order CH x+1 + CH z–1 reactions are less competitive compared with the direct dehydrogenation of CH x . Both DFT calculations and microkinetic model demonstrate that the reaction CH + CH → C2H2 is a major channel to produce C2H y at a temperature of 860 °C, followed by CH3 + CH → C2H4. When the H2 influence is introduced, the major intermediate changes from CH to CH3 on Cu(100) surface with the increase of H2 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.

Molecular understandings on the activation of light hydrocarbons over heterogeneous catalysts

“… 46 It further results in that the D4 barrier is only 62 kJ mol –1 on Ni(100), much lower than the barrier on Ni(111), which is >120 kJ mol –1 . Similar stabilization of adsorbed carbon atom and low barriers of D4 steps were also observed on Cu(100) 50 , 65 and Rh(100). 51…”

First-principles investigation of the dissociation and coupling of methane on small copper clusters: Interplay of collision dynamics and geometric and electronic effects

“…This is in agreement with reports which claim CH 3 to be a more dominant species compared to CH in graphene growth on Cu(100) surface at high partial pressure of hydrogen. 84 An exhaustive investigation of other hydrocarbon intermediates that may be involved in the formation of larger hydrocarbons via coupling of various CH x surface species is beyond the scope of this report.…”