Regulation of Oxygen Activation Pathways to Optimize Photocatalytic Methane Oxidative Coupling Selectivity

Photocatalytic oxidative coupling of methane (POCM) is a direct way for the methane transformation into ≥C2 alkanes. However, the typical oxygen activation path often leads to the formation of strong oxidizing superoxide radical (O₂^–) species, which makes the whole reaction face serious selectivity problems. Herein, we constructed N and oxygen vacancy dual active sites on TiO₂{001} nanosheets (TiO₂–NV_o) to regulate the oxygen activation pathway and achieve a high activity and selectivity of photocatalytic OCM. Compared with ordinary Au/TiO₂{001} nanosheets, the alkane yields of Au/TiO₂–NV_o are increased from 16 μmol h^–1 to 32 μmol h^–1, and the selectivity of alkanes increased from 61% to 93%. The performance is superior when compared with the reported till date in photocatalytic OCM in batch reactors. The superior performance originates from the unique N–V_o dual active sites for synergistically cleaving the detrimental O₂^– into desirable mono-oxygen active species (O^·–) to suppress undesired overoxidation reaction. The formed O^·– species from O₂^– dissociation, in turn, is active for the selective H abstraction of CH₄ into •CH₃ to improve the subsequent C–C coupling reaction on the Au nanocluster surface. This work provides a new approach of O₂ dissociation to address the overoxidation of methane in an aerobic environment for achieving highly selective CH₄ conversion.