Reaction pathway of CH4/CO2 reforming over Ni8/MgO(100)

First-principles calculations depended on density functional theory have been employed to explore the reaction mechanism of CH4/CO2 reforming on Ni/MgO catalyst. The Ni8 cluster supported on the MgO(100) slab has been used to model the Ni/MgO catalyst. CO2 can decompose on a Ni8 cluster and produce O species through either direct dissociation or hydrogenated dissociation. As a key intermediate produced by CH4 dissociation, CH2 could be oxygenated by O species (atomic O or OH), generating CH2O or CH2OH; or dehydrogenate into CH, which is then oxygenated by atomic O, resulting in the CHO dissociating. These three pathways can occur in parallel because of the similar energy barrier of their rate-determining steps (less than 0.1 eV). Furthermore, the formation and removal of surface carbon have been analyzed at length. Atomic H from CH,, decomposition has the best reactivity to surface C elimination, followed by O and OH species.