Efficiently Light-Driven Nonoxidative Coupling of Methane on Ag/NaTaO₃: A Case for Molecular-Level Understanding of the Coupling Mechanism

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Metal-decorated oxide semiconductors are overwhelming photocatalysts for nonoxidative coupling of methane (NOCM). However, the overall NOCM mechanism remains an unopened black box, which hinders the design of high-performance catalysts. Herein, we systematically studied a series of noble metal (Ag, Au, Pt, Pd, Cu, and Ni)-decorated oxides (NaTaO 3, CaTiO 3, LiNbO 3, and TiO 2 ) for NOCM. We proposed that the active sites for H abstraction and C–C coupling of CH 4 are spatially separated. Specifically, NaTaO 3 only completes the initial H abstraction of CH 4 activation, while metal nanoparticles are responsible for the final C–C coupling. Noble metals dominate NOCM by significantly decreasing the energy barrier of CH 4 dissociation and promoting C–C coupling. Among various metals, Ag is preferential for the weak adsorption of · CH 3 intermediates and subsequent metal-induced C–C coupling. This contributes to Ag/NaTaO 3 the highest C 2 H 6 yield of 194 μmol g –1 h –1 and stoichiometric H 2 with 11.2% quantum efficiency. This work provides a molecular-level insight into the CH 4 coupling mechanism on metal-decorated photocatalysts.