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 (O-2(-)) 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-NVo) 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-NVo are increased from 16 mu mol h(-1) to 32 mu mol 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 O-2(-) into desirable mono-oxygen active species (O-) to suppress undesired overoxidation reaction. The formed O- species from O-2(-) dissociation, in turn, is active for the selective H abstraction of CH4 into center dot CH3 to improve the subsequent C-C coupling reaction on the Au nanocluster surface. This work provides a new approach of O-2 dissociation to address the overoxidation of methane in an aerobic environment for achieving highly selective CH4 conversion.