A selective Au-ZnO/TiO2 hybrid photocatalyst for oxidative coupling of methane to ethane with dioxygen

Direct oxidation of methane to valuable chemicals is a great challenge as catalysts with both high activity and selectivity for the activation of inert C-H bonds are required. Here, we report the highly efficient and selective photo-oxidation of methane to ethane with dioxygen in a flow reactor using a Au nanoparticle (NP) loaded ZnO/TiO2 hybrid. An ethane production rate of over 5,000 mu mol g(-1) h(-1) with 90% selectivity is achieved, which is more than one order of magnitude higher than the state-of-the-art photocatalytic systems. Detailed characterizations and theoretical studies show that the formation of heterojunctions between ZnO and TiO2 leads to enhanced photocatalytic activity, while maintaining high selectivity owing to the weak overoxidation ability of the main component ZnO. Moreover, the Au cocatalyst enables the facile desorption of methyl (CH3) species as (CH3)-C-center dot radicals in the gas phase, thereby facilitating C2H6 formation and inhibiting overoxidation of CH4 to CO2.

Automated summary

The study presents a highly efficient and selective photo-oxidation method for the direct conversion of methane to ethane using a Au nanoparticle (NP) loaded ZnO/TiO2 hybrid. This method achieves an ethane production rate of over 5,000 mu mol g(-1) h(-1) with 90% selectivity, which is more than an order of magnitude higher than current state-of-the-art photocatalytic systems. The enhanced photocatalytic activity is attributed to the formation of heterojunctions between ZnO and TiO2, while the Au cocatalyst facilitates C2H6 formation and inhibits overoxidation of CH4 to CO2.