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Hydrogen peroxide (H₂O₂) is an important chemical as it is an environmentally friendly oxidant for organic synthesis and environmental remediation as well as a promising candidate for the liquid fuel. Photocatalytic generation of H₂O₂ is sustainable, and many efforts have been put into the development of new catalysts to gain high H₂O₂ yields. In this investigation, Au/ZnO, Ag/ZnO and Au-Ag/ZnO catalysts were prepared by the simultaneous impregnation of HAuCl₄ and AgNO₃ and they were used to generate H₂O₂ from a methanol/O₂ system. It was demonstrated that Au/ZnO had the best performance at generating H₂O₂. The presence of Au on ZnO accelerated the generation of H₂O₂ on ZnO and facilitated H₂O₂ adsorption onto the catalyst surface, which resulted in the reaction kinetics changing from zero-order to first-order. Ag atoms on Ag/ZnO were unstable and would strip from the surface of ZnO during irradiation, decreasing the yield of H₂O₂. The stabilization of Ag on Au-Ag/ZnO depended on the ratio of Au and Ag. Au_0.1Ag_0.2/ZnO was a stable catalyst and it showed that the presence of Ag promoted the formation and decomposition of peroxide, simultaneously.