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

Abstract

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 microkinetic model demonstrate that the reaction CH + CH → C2H2 is a major channel to produce C2Hy 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 w...