Unraveling the Synergy of Au and Polar MgO(111) Surface in Photothermal Catalytic Oxidative Coupling of Methane

Abstract Direct and selective catalytic oxidative coupling of methane (OCM) into high‐carbon products is a great challenge in C1 chemistry. Herein, the successful fabrication of a series of Au clusters loaded on different MgO facets of (111), (110), and (100) is reported. This work demonstrates the Au‐loaded MgO(111) (denoted as Au/MgO(111)) shows the highest C₂H₆ yield of 12733.4 µmol g⁻¹ h⁻¹ and selectivity of 90.4%, which is 2.46 times higher than that of Au/MgO(110) (5171.4 µmol g⁻¹ h⁻¹) and 25.14 times higher than that of Au/MgO(100) (506.4 µmol g⁻¹ h⁻¹). Moreover, the high activity of Au/MgO(111) can be well maintained over 100 h. Detailed in situ experiments and theoretical calculation reveal such great performance can be attributed to 1) the strong electronic affinity of the surface oxygen species on polar MgO(111) and CH₄with the lowest adsorption energy of −0.82 eV; 2) the Au/MgO(111) shows the lowest ΔE_RDS of 0.53 eV in the rate‐deterime step of OCM that comes in activating the second CH₄ molecule; 3) the Au can act as a hole acceptor under light irradiation and adsorb *CH₃ with a strong d‐σ hybridization, resulting in an increased C₂H₆ selectivity.