Strategies to Improve the Activity While Maintain the Selectivity of Oxidative Coupling of Methane at La2O3: A Density Functional Theory Study

Oxidative coupling of methane (OCM) holds the promise to achieve high value-added products directly from methane, and the strategies to improve the catalytic performance of this process are highly desired. In this work, we performed extensive density functional theory (DFT) calculations to systematically study the activity and selectivity of the OCM reactions on several types of the La2O3 and CeO2 catalysts. We theoretically evidenced that the La2O3 catalyst has high hydrocarbon selec-tivity but low activity, while the CeO2 shows an opposite performance. These results can be largely rationalized by the calcu-lated reaction energetics in generating the key CH3· intermediates and further protecting them from excessive oxidation on the surface. We then proposed two strategies to improve the OCM activity while maintain the selectivity of the La2O3 catalyst. Geometrically, by constructing the stepped La2O3(210) surface exposing lattice oxygens with low coordination numbers, both the heterolytic cleavage of the...