Investigation the active site of methane dissociation on Ni-based catalysts: A first-principles analysis

The adsorption and dissociation Of CH4 oil clean Ni(1 0 0), oxygen atom pre-adsorbed Ni(1 0 0) and NiO(1 0 0) surfaces have been Studied using density functional theory calculations with the periodic slab model. The activation barrier For methane dissociation oil clean Ni(1 0 0) is much lower than that oil the oxygen arom pre-adsorbed Ni(1 0 0) and NiO(1 0 0) surface. Thus the active site for methane dissociation is the metallic Ish instead of the oxidized Ni. Moreover, the decomposition of activation barrier has been performed. The result further explains how the existence of oxygen atom increases the barrier Though the pre-adsorbed oxygen atom decreases the interaction between CH3 and H in the transition slate. it greatly decreases the interaction of CH3 and H With Substrate. So the overall result is that the oxygen atom inhibits the dissociation of methane on Ni surface Importantly, it was found that a three-center bond formed in the transition state when oxygen atom acts as a spectator. which leading to a smaller energy barrier for the reaction of CH4 + O -> CH3 (+) H + O than that of CH4 + O -> CH3 + OH. (C) 2009 Elsevier B.V. All rights reserved.