The Au/MnOx/TiO2 catalyst was used for the photocatalytic oxidation of carbon monoxide. The catalytic activity of Au/MnOx/TiO2 with low concentration of manganese (3-7 mol%) was much higher than that of Au/TiO2. The surface of Au/MnOx/TiO2 was characterized by XPS and Raman spectroscopy. While the main state ofmanganese in 13.8 mol% MnO x/TiO2 was Mn4+ species, Mn3+ was the dominant species in the samples with below 6.5 mol% manganese. Raman spectroscopy revealed that the interaction between the MnOx and TiO2 form Mn-O-Ti species in which the state of manganese was Mn 3+. The Au particles also interacted with both MnOx and TiO2 to modify the surface of them. In the case of the Au species, low loading of manganese produced the metallic Au0 and perimeter interfacial Auδ+, whereas high loading showed the coexistence of three components which were metallic Au0, perimeter interfacial Auδ+, and oxidic Au3+. The catalytic active component was the metallic Au0 and perimeter interfacial Au δ+7 species, which were dispersed on TiO2 and Mn3+/TiO2.
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