Photocatalytic Oxidative Coupling of Methane to Ethane Using Water and Oxygen on Ag₃PO₄-ZnO

Photocatalytic oxidative coupling is an effective way of converting CH₄ to high-value-added multi-carbon chemicals under mild conditions, where the breaking of the C-H bond is the main rate-limiting step. In this paper, the Ag₃PO₄-ZnO heterostructure photocatalyst was synthesized for photocatalytic oxidative coupling of methane (OCM) to C₂H₆. In addition, an excellent C₂H₆ yield (16.62 mmol g^-1 h^-1) and a remarkable apparent quantum yield (15.8% at 350 nm) at 49:1 CH₄/Air and 20% RH are obtained, which is more than three times that of the state-of-the-art photocatalytic systems. Ag₃PO₄ improves the adsorption and dissociation ability of O₂ and H₂O, benefiting the formation of surface hydroxyl species. As a result, the C-H bond activation energy of CH₄ on ZnO was obviously reduced. Meanwhile, the improved separation of photogenerated carriers on the Ag₃PO₄-ZnO heterostructure also accelerates the OCM process. Moreover, Ag nanoparticles (NPs) derived from Ag₃PO₄ reduction by photoelectrons promote the coupling of *CH₃, which can inhibit the overoxidation of CH₄ and increase C₂H₆ selectivity. This research provides a guide for the design of catalyst and reaction systems in the photocatalytic OCM process.