Photocatalytic Oxidative Coupling of Methane over Au Ag Single-Atom Alloy Modified ZnO with Oxygen and Water Vapor: Synergy of Gold and Silver.

C-H dissociation and C-C coupling are two key steps in converting CH into multi-carbon compounds. Here we report a synergy of Au and Ag to greatly promote C H formation over Au Ag single-atom alloy nanoparticles (Au Ag NPs)-modified ZnO catalyst via photocatalytic oxidative coupling of methane (POCM) with O and H O. Atomically dispersed Au in Au Ag NPs effectively promotes the dissociation of O and H O into *OOH, promoting C-H activation of CH on the photogenerated O to form *CH . Electron-deficient Au single atoms, as hopping ladders, also facilitate the migration of electron donor *CH from ZnO to Au Ag NPs. Finally, *CH coupling can readily occur on Ag atoms of Au Ag NPs. An excellent C H yield of 14.0 mmol g  h with a selectivity of 79 % and an apparent quantum yield of 14.6 % at 350 nm is obtained via POCM with O and H O, which is at least two times that of the photocatalytic system. The bimetallic synergistic strategy offers guidance for future catalyst design for POCM with O and H O.