Efficient hole abstraction for highly selective oxidative coupling of methane by Au-sputtered TiO2 photocatalysts

Photocatalytic oxidative coupling of methane (OCM) produces C-2 molecules that can be used as building blocks for synthesis of fuels and chemicals. However, the yield rate and the selectivity of C-2 products are still moderate due to the stable nature of methane molecules. Here we develop a Au nanocluster-loaded TiO2 photocatalyst by a sputtering approach, achieving a high methane conversion rate of 1.1 mmol h(-1), C-2 selectivity of similar to 90% and apparent quantum efficiency of 10.3 +/- 0.6%. The high C-2/C2+ yield rate is on the same order of magnitude as the benchmark thermal catalysts in OCM processes operated at high temperature (>680 degrees C). Au nanoparticles are shown to prolong TiO2 photoelectron lifetimes by a factor of 66 for O-2 reduction, together with Au acting as a hole acceptor and catalytic centre to promote methane adsorption, C-H activation and C-C coupling. This work underscores the importance of multifunctional co-catalysts and mechanistic understanding to improve photocatalytic OCM.