MgO Nanostructures on Au(111) as Catalysts for Low-Temperature Methane Activation and C-C Coupling

The selective conversion of methane (CH₄) under mild conditions remains challenging due to strong C-H bonds and catalyst coking. We systematically investigated submonolayer MgO nanostructures on Au(111), where two-dimensional (2D) MgO islands with stable Mg-O-Au interfaces catalyze low-temperature CH₄ activation and C-C coupling. Upon CH₄ exposure at 300 K, surface-bound CH_x and C₂H_x intermediates formed and persisted postevacuation, indicating robust CH_x-O-Mg linkages. Temperature-programmed studies revealed that C-H activation and C-C coupling intensify with heat: the CH_x signal grew continuously while the C₂H_x signal reached a plateau at 400-500 K. O 1s and Mg 2p attenuation confirmed adsorption of the hydrocarbons on MgO. Catalytic tests at 500 K yielded C₂H₆ (70%) and C₂H₄ (30%) without coking, underscoring MgO's role as an active catalyst. These results offer new design principles for developing coke-resistant and low-temperature methane upgrading catalysts.