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 semiconductor generates electrons under irradiation to produce H2O2 from O2, in which the photo-induced holes could activate CH4 to form •CH3. The Au served as a co-catalyst for activating CH4, while the Fe2+ species catalyzed Fenton-like reactions by activating H2O2 to form •OH radicals, followed by reacting with •CH3 to produce CH3OH. The synergetic effects of Au, Fe, and ZnO result in a high CH3OH yield of 1365 μmol·g−1·h−1 with high CH3OH selectivity of up to 90.7%.