Oxygen-Promoted Methane Activation on Copper

The role of oxygen in the activation of C–H bonds in methane on clean and oxygen-precovered Cu(111) and Cu₂O­(111) surfaces was studied with combined in situ near-ambient-pressure scanning tunneling microscopy and X-ray photoelectron spectroscopy. Activation of methane at 300 K and “moderate pressures” was only observed on oxygen-precovered Cu(111) surfaces. Density functional theory calculations reveal that the lowest activation energy barrier of C–H on Cu(111) in the presence of chemisorbed oxygen is related to a two-active-site, four-centered mechanism, which stabilizes the required transition-state intermediate by dipole–dipole attraction of O–H and Cu–CH₃ species. The C–H bond activation barriers on Cu₂O­(111) surfaces are large due to the weak stabilization of H and CH₃ fragments.