Enhanced Photocatalytic Oxidative Coupling of Methane over Metal-Loaded TiO Nanowires.

The photocatalytic oxidative coupling of methane (OCM) on metal-loaded one-dimensional TiO nanowires (TiO NWs) was performed. With metal loading, the electric and optical properties of TiO NWs were adjusted, contributing to the improvement of the activity and selectivity of the OCM reaction. In the photocatalytic OCM reaction, the 1.0 Au/TiO NW catalyst exhibits an outstanding CH production rate (4901 μmol g h) and selectivity (70%), alongside the minor production of CH and CH, achieving a total C-C hydrocarbon selectivity of 75%. In contrast, catalysts loaded with Ag, Pd, and Pt show significantly lower activity, with Pt/TiO NWs producing only CO, indicating a propensity for the deep oxidation of methane. The O-TPD analyses reveal that Au facilitates mild O adsorption and activation, whereas Pt triggers excessive oxidation. Spectroscopic and kinetic studies demonstrate that Au loading not only enhances the separation efficiency of photogenerated electron-hole pairs, but also promotes the generation of active oxygen species in moderate amounts, which facilitates the formation of methyl radicals and their coupling into CH while suppressing over-oxidation to CO. This work provides novel insights and design strategies for developing efficient photocatalysts.