We use density functional theory to examine the dissociative adsorption of methane on two irreducible oxides: MgO and La2O3. In the case of La2O3 we show that the dissociation mechanism is very unusual because of the peculiar structural motif made by the La ions in this oxide. The dissociation is heterolytic and the most favorable configuration is one in which CH3 donates an electron to form a polaron consisting of an electron located inside a pyramid formed by four La ions near the surface; the hydrogen atom moves inside the pyramid to capture the electron donated by CH3 and form a “hydride”. We also examine the how the dissociative chemisorption of methane is affected by the presence of an O2 molecule adsorbed on the surface of TiO2 or on a stepped MgO surface. In both cases, the oxygen acts as an electron acceptor that facilitates methane dissociation on the surface.

Methane activation by oxide catalysts: The role of coadsorption

253rd National Meeting (2017)

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