Hierarchical Heterogeneity at the CeO_x–TiO₂ Interface: Electronic and Geometric Structural Influence on the Photocatalytic Activity of Oxide on Oxide Nanostructures

Mixed oxide interfaces are critical for delivering active components of demanding catalytic processes such as the photocatalytic splitting of water. We have studied CeOx–TiO2 catalysts with low ceria loadings of 1, 3, and 6 wt % that were prepared with wet impregnation methods to favor a strong interaction between CeOx and TiO2. In these materials the interfaces between CeOx–TiO2 have been sequentially loaded (1%, 3%, and 6%), with and without Pt (0.5 wt %). The structure and properties of the catalysts were characterized using several X-ray and electron based techniques including XRD, XPS, UPS, NEXAFS, UV–vis, and HR-STEM/STEM-EELS to unravel the local morphology, bulk structure, surface states, and electronic structure. The combination of all these techniques allows us to analyze in a systematic way the complete structural and electronic properties that prevail at the CeOx–TiO2 interface. Fluorite structured nanocrystallites of ceria on anatase-structured titania were identified by both XRD and NEXAFS. ...