Bimetallic (Au–Cu core)@(ceria shell) nanotubes for photocatalytic oxidation of benzyl alcohol: improved reactivity by Cu

Supported bimetallic nanocomposites are promising in photocatalysis due to the multi-component interaction between metals and between metals and carriers. By an in situ reduction method, a series of monometallic (Au@CeO2 and Cu@CeO2) and bimetallic catalysts (Au8Cu2@CeO2, Au5Cu5@CeO2 and Au1Cu9@CeO2) are obtained, with a metallic core and a CeO2 shell structure. The in situ reduction method developed in this work is a one-step strategy to obtain supported multi-component nanomaterials with a core–shell structure. Photo-assisted oxidation of benzyl alcohol to benzaldehyde was performed over the above samples, and the reactivity presented a parabolic plot with the increase of Cu content, reaching the summit for Au1Cu9@CeO2. Inpouring of Cu enlarged the specific surface area and generated more oxygen vacancies, which are significant for improving the photocatalytic performance. The intimate correlation between the reactivity and the concentration of the oxygen vacancies provides that the surface of the CeO2 support with a large number of oxygen vacancies serves as the active site for aerobic oxidation. Accordingly, a mechanism is proposed for the photocatalytic efficiency enhancement as the function of the Cu concentration. Particularly, the catalyst Au1Cu9@CeO2 containing quite a low amount of Au species demonstrated the best catalytic activity and high selectivity and stability, which is strongly desired for cost-effective catalysts.