Efficient hole abstraction for highly selective oxidative coupling of methane by Au-sputtered TiO2 photocatalysts
Xiyi Li, Chao Li, Youxun Xu, Qiong Liu, Mounib Bahri, Liquan Zhang, Nigel D. Browning, Alexander J. Cowan, Junwang Tang
Abstract
Abstract 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 TiO 2 photocatalyst by a sputtering approach, achieving a high methane conversion rate of 1.1 mmol h −1 , C 2 selectivity of ~90% and apparent quantum efficiency of 10.3 ± 0.6%. The high C 2 /C 2+ yield rate is on the same order of magnitude as the benchmark thermal catalysts in OCM processes operated at high temperature (>680 °C). Au nanoparticles are shown to prolong TiO 2 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.