Photocatalytic O2 oxidation of CH4 to CH3OH on AuFe-ZnO bifunctional catalyst

Selective oxidation of CH4 by O2 to produce CH3OH under mild reaction conditions is of importance but remains a significant challenge. Herein, we report a novel nanocomposite of highly dispersed Au and Fe species on ZnO (AuFe-ZnO). During photocatalytic O2 oxidation of CH4 to CH3OH, this AuFe-ZnO acts as a bifunctional catalyst to drive one-pot cascade reactions (O2 + H2O-* H2O2 and CH4 + H2O2-* CH3OH + H2O). The ZnO semi-conductor generates electrons under irradiation to produce H2O2 from O2, in which the photo-induced holes could activate CH4 to form center dot CH3. The Au served as a co-catalyst for activating CH4, while the Fe2+ species catalyzed Fenton-like reactions by activating H2O2 to form center dot OH radicals, followed by reacting with center dot CH3 to produce CH3OH. The synergetic effects of Au, Fe, and ZnO result in a high CH3OH yield of 1365 mu mol center dot g- 1 center dot h-1 with high CH3OH selectivity of up to 90.7%.