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Correlation of Methane Activation and Oxide Catalyst Reducibility and Its Implications for Oxidative Coupling

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journal contribution
posted on 04.02.2016 by Gaurav Kumar, Sai Lap Jacky Lau, Matthew D. Krcha, Michael J. Janik
We investigate methane activation over a range of metal-oxide surfaces. Density functional theory calculations are used to correlate the C–H bond activation energy to the surface reducibility (oxygen vacancy formation energy, work function). The correlation includes several reducible and nonreducible metal-oxides, doped CeO2, doped TiO2, ZnO, and doped MgO, and also holds for various oxidation states of TbOx, different surface facets of TiO2, and variation of Hubbard U parameter for CeO2. We find a linear correlation between the C–H activation reaction energy, ·CH3 adsorption energy, and the oxygen vacancy formation energy of pure/doped metal-oxides, making surface reducibility a descriptor for predicting catalyst activity and selectivity against further oxidation of the ·CH3 radical.