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

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 (NaTaO3, CaTiO3, LiNbO3, and TiO2) for NOCM. We proposed that the active sites for H abstraction and C-C coupling of CH4 are spatially separated. Specifically, NaTaO3 only completes the initial H abstraction of CH4 activation, while metal nanoparticles are responsible for the final C-C coupling. Noble metals dominate NOCM by significantly decreasing the energy barrier of CH4 dissociation and promoting C-C coupling. Among various metals, Ag is preferential for the weak adsorption of center dot CH3 intermediates and subsequent metal-induced CC coupling. This contributes to Ag/NaTaO3 the highest C2H(6) yield of 194 mu mol g-1 h(-1) and stoichiometric H-2 with 11.2% quantum efficiency. This work provides a molecular-level insight into the CH4 coupling mechanism on metal-decorated photocatalysts.