Synergistic Au and ZnO Sites Decorated on TiO 2 Steering Methane Photocatalytic Oxidative Coupling to Ethane

The selective photocatalytic oxidative coupling of methane (OCM) offers a mild route to ethane synthesis but usually suffers from low yields and CH 4 overoxidation. Here, Au and ZnO nanoparticles decorated on TiO 2 were designed as active and stable catalysts to realize efficient C–H dissociation and selective C–C coupling. The optimal Au–ZnO/TiO 2 (metal loadings: 1.5% Au and 1.0% ZnO) catalyst achieved a high C 2 H 6 production rate of 17.02 mmol g –1 h –1 at a superior selectivity of 90.1% under xenon lamp irradiation and further maintained a stable activity for 120 h. This result significantly outperformed the most active Au- and Ag-supported photocatalysts reported to date in the literature. Physical and photoelectronic characterizations, in situ spectroscopy, and DFT calculations revealed Au and ZnO as the essential active sites for the OCM-to-C 2 H 6 reaction, and their synergism is responsible for the outstanding performance. Small Au and ZnO nanoparticles (ca. 2–3 nm) decorated on TiO 2 can enhance light harvesting, accelerate charge separation, and prolong carrier lifetime. CH 4 and O 2 were found to adsorb and activate on Au and ZnO sites to forming •CH 3 and •O 2 – /•O – reactive intermediates, sustaining the photocatalytic OCM. ZnO was shown to obviously reduce the energy barrier for C–H cleavage and promote O 2 dissociation at oxygen vacancy, while electron-rich Au was disclosed to facilitate •CH 3 migration and C–C coupling via lower barriers. Therefore, the synergistic catalysis between Au and ZnO primely overcomes the activity-selectivity trade-off and enables high C 2 H 6 production by suppressing CH 4 overoxidation to CO 2 .