Mechanisms of Transforming CHx to CO on Ni(111) Surface by Density Functional Theory

Abstract

To elucidate feasible routes of producing CO from CH 3 and unravel the effect of adsorbed O on CH x transformation, the reactivity of CH x (x = 1-3) with and without the assistance of adsorbed atomic O on Ni(111) was explored using density functional theory calculations. The adsorption energies of CH x (x = 0-3) were found to be significantly reduced on an O-preadsorbed Ni(111) surface compared to a pure surface. Furthermore, O-assisted one-step dehydrogenation of CH x (x = 1-3) features energy barriers and thus is difficult to proceed. In terms of energy, the direct dissociation of CH 3 is favorable, except for the last CH dehydrogenation, which is energy intensive. Interestingly, in O-assisted two-step CH transformation to CO via CHO intermediate, the barrier is dramatically lowered. The successive dehydrogenations of CH x O (x = 1-3) were also found to be a route for CO formation. Finally, two possible pathways from CH 3 to CO are proposed: (a) CH 3 → CH 2 → CH → CHO → CO;