Low-Temperature Activation and Coupling of Methane on MgO Nanostructures Embedded in Cu2O/Cu(111)

The efficient conversion of methane into valuable hydrocarbons, such as ethane and ethylene, at relatively low temperatures without deactivation issues is crucial for advancing sustainable energy solutions. Herein, AP-XPS and STM studies show that MgO nanostructures (0.2–0.5 nm wide, 0.4–0.6 Å high) embedded in a Cu2O/Cu(111) substrate activate methane at room temperature, mainly dissociating it into CHx(x= 2 or 3) and H adatoms, with minimal conversion to C adatoms. These MgO nanostructures in contact with Cu2O/Cu(111) enable C–C coupling into ethane and ethylene at 500 K, a significantly lower temperature than that required for bulk MgO catalysts (>700 K), with negligible carbon deposition and no deactivation. DFT calculations corroborate these experimental findings. The CH4,gas→ *CH3+ *H reaction is a downhill process on MgO/Cu2O/Cu(111) surfaces. The activation of methane is facilitated by electron transfer from copper to MgO and the existence of Mg and O atoms with a low coordination number in the oxide nanostructures. The formation of O–CH3and O–H bonds overcomes the energy necessary for the cleavage of a C–H bond in methane. DFT studies reveal that smaller Mg2O2model clusters provide stronger binding and lower activation barriers for C–H dissociation in CH4, while larger Mg3O3clusters promote C–C coupling due to weaker *CH3binding. All of these results emphasize the importance of size when optimizing the catalytic performance of MgO nanostructures in the selective conversion of methane.