Hierarchical Heterogeneity at the CeOx鈥揟iO2 Interface: Electronic and Geometric Structural Influence on the Photocatalytic Activity of Oxide on Oxide Nanostructures

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• 作者：Si Luo ; Thuy-Duong Nguyen-Phan ; Aaron C. Johnston-Peck ; Laura Barrio ; Shawn Sallis ; Dario A. Arena ; Shankhamala Kundu ; Wenqian Xu ; Louis F. J. Piper ; Eric A. Stach ; Dmitry E. Polyansky ; Etsuko Fujita ; Jos茅 A. Rodriguez ; Sanjaya D. Senanayake
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：February 5, 2015
• 年：2015
• 卷：119
• 期：5
• 页码：2669-2679
• 全文大小：705K
• ISSN：1932-7455

文摘

Mixed oxide interfaces are critical for delivering active components of demanding catalytic processes such as the photocatalytic splitting of water. We have studied CeO_x鈥揟iO₂ catalysts with low ceria loadings of 1, 3, and 6 wt % that were prepared with wet impregnation methods to favor a strong interaction between CeO_x and TiO₂. In these materials the interfaces between CeO_x鈥揟iO₂ 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鈥搗is, 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 CeO_x鈥揟iO₂ interface. Fluorite structured nanocrystallites of ceria on anatase-structured titania were identified by both XRD and NEXAFS. A sequential increase of the CeO_x loading led to the formation of clusters, then plates, and finally nanoparticles in a hierarchical manner on the TiO₂ support. The electronic structures of these catalysts indicate that the interaction between TiO₂ and CeO₂ is closely related to the local morphology of nanostructured CeO₂. Ce³⁺ cations were detected at the surface of CeO₂ and at the interface of the two oxides. In addition, the titania is perturbed by the interaction with ceria and also with Pt. The photocatalytic activity for the splitting of H₂O using UV light was measured for these materials and correlated with our understanding of the electronic and structural properties. Optimal catalytic performance and photoresponse results were found for the 1 wt % CeO_x鈥揟iO₂ catalyst where low dimensional geometry of the ceria provided ideal electronic and geometrical properties. The structural and electronic properties of the interface were critical for the photocatalytic performance of this mixed-oxide nanocatalyst system.