Density functional theory studies on the mechanism of activation of methane by homonuclear bimetallic Ni–Ni

Abstract

The reaction mechanisms of methane catalyzed by homonuclear bimetallic Ni–Ni have been investigated theoretically in this paper. Activation of methane by homonuclear bimetallic Ni–Ni is proposed to proceed in two effective catalytic reaction routes, Route I and Route II. The homonuclear bimetallic Ni–Ni inserts in the C–H bond to form the ring-hydride and chain-hydride in Route I and Route II, respectively. In this study, we examine the isomerization reaction pathway for ring-hydride (Route I). Undergoing the isomerization reaction, the chain-product CH3Ni–Ni–H is formed. From the chain-hydride CH3Ni2–H, two kinds of distinguishable reaction paths have been considered including isomerization reaction and H2 elimination reactions in Route II. The H2 elimination reactions are proposed to proceed along three parallel reaction pathways with the activation of the second C–H bond on the potential energy surfaces (PESs). The pathway of rearranging to isomer in Route II is preferred to the others. In comparison with heteronuclear bimetallic NiM+ (M=Cu, Ag) and homonuclear bimetallic Pt2+, the dehydrogenation of methane induced by homonuclear bimetallic Ni–Ni should be more favored thermodynamically and should give more branching.