Photocatalytic Oxidative Coupling of Methane over SrTiO3 Overlayers on Au Nanoparticles

Photocatalytic oxidative coupling of methane (OCM) is a prevailing method to access multicarbon (C2+) 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 SrTiO3 supported, SrTiO3 overlayer coated Au nanoparticles (Au@SrTiO3). The SrTiO3 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 SrTiO3 overlayers on Au nanoparticles (NPs). The Au@SrTiO3 catalyst is stable for more than 300 h, affording C2H6 with a formation rate of 155 μmol h-1, 7 times that of Au/SrTiO3 without SrTiO3 overlayers. The activity is improved to 1050 μmol h-1 with a C2+ selectivity of 94% by increasing Au@SrTiO3 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.