Buffered Hydroxyl Radical for Photocatalytic Non‐Oxidative Methane Coupling

Hydroxy radical (•OH) is a prestigious oxidant that allows the cleavage of strong chemical bonds of methane but is untamed, leading to over‐oxidation of methane and waste of oxidants, especially at high methane conversion. Here, we managed to buffer •OH in an aqueous solution of photo‐irradiated Fe3+, where •OH almost participates in methane oxidation. Due to the interaction between Fe3+ and SO42−, the electron transfer from OH− to excited‐state Fe3+ for •OH generation is retarded, while excessive •OH is consumed by generated Fe2+ to restore Fe3+. When combined with a Ru/SrTiO3:Rh photocatalyst, the buffered •OH converts methane to C2+ hydrocarbons and H2 with formation rates of 246 and 418 μmol h−1, respectively. The apparent quantum efficiency reaches 13.0 ± 0.2%, along with 10.2% methane conversion and 81% C2+ selectivity after 80 hours of reaction. Overall, this work presents a strategy for controlling active radicals for selective and efficient photocatalysis.