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Title: Hierarchical Heterogeneity at the CeO x –TiO 2 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 photo-catalytic splitting of water. We have studied CeOxTiO₂ catalysts with low ceria loadings of 1 wt%, 3 wt% 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 allow us to analyze in a systematic way the complete structural and electronic properties that prevail at the CeOx-TiO₂ interface. Fluorite structured nano crystallites of ceria on anatase-structured titania were identified by both XRD and NEXAFS. A sequential increasing of the CeOx loading led to the formation of clusters, then plates and finally nano particles 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 morphologymore » 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 photo response results were found for the 1 wt% CeOx-TiO₂ 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.« less
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [1] ;  [1] ;  [4] ;  [2] ;  [1] ;  [1] ;  [1] ;  [1]
  1. Brookhaven National Lab. (BNL), Upton, NY (United States). Chemistry Dept.
  2. Brookhaven National Lab. (BNL), Upton, NY (United States). Center for Functional Nanomaterials
  3. Consejo Superior de Investigaciones Cientificas (CSIC), Madrid (Spain). Inst. de Catalisis y Petroleoquimica
  4. Binghamton Univ., NY (United States). Materials Science & Engineering, Dept. of Physics, Applied Physics and Astronomy
  5. Brookhaven National Lab. (BNL), Upton, NY (United States). Photon Sciences Division
Publication Date:
OSTI Identifier:
1183830
Report Number(s):
BNL--107851-2015-JA
Journal ID: ISSN 1932-7447; R&D Project: CO026; KC0304030
Grant/Contract Number:
SC00112704
Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 119; Journal Issue: 5; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY mixed-metal oxide catalysts; nanostructure materials; photocatalytic water splitting; ceria-titania; transmission electron microscopy; x-ray absorption; x-ray photoelectron spectroscopy