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

Abstract The adsorption and dissociation of CH 4 on 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 on clean Ni(1 0 0) is much lower than that on the oxygen atom pre-adsorbed Ni(1 0 0) and NiO(1 0 0) surface. Thus the active site for methane dissociation is the metallic Ni 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 CH 3 and H in the transition state, it greatly decreases the interaction of CH 3 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 CH 4  + O → CH 3  + H + O than that of CH 4  + O → CH 3  + OH.