Photocatalytic Oxidative Coupling of Methane over SrTiO ₃ Overlayers on Au Nanoparticles

Photocatalytic oxidative coupling of methane (OCM) is a prevailing method to access multicarbon (C 2+ ) hydrocarbons. However, the kinetically slow C–C coupling of the methyl radical hinders the overall methane coupling reaction and leads to overoxidation side reactions. Here we report photocatalytic OCM over SrTiO 3 supported, SrTiO 3 overlayer coated Au nanoparticles (Au@SrTiO 3 ). The SrTiO 3 support and overlayers capture photogenerated holes to activate the methane C–H bond. C–C coupling between the methyl radical intermediate is rate limiting and occurs with an improved selectivity of 93% over the SrTiO 3 overlayers on Au nanoparticles (NPs). The Au@SrTiO 3 catalyst is stable for more than 300 h, affording C 2 H 6 with a formation rate of 155 μmol h –1, 7 times that of Au/SrTiO 3 without SrTiO 3 overlayers. The activity is improved to 1050 μmol h –1 with a C 2+ selectivity of 94% by increasing Au@SrTiO 3 loading to harvest more light. These figures of merits are comparable with the benchmarking photocatalysts for OCM by elucidating the chemistry of C–C coupling sites.