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Preparation and structural characterization by XRD and XAS of the supported gold catalysts

M. LAZAR1, V. ALMASAN1, S.PINTEA1, B. BARZ2,* , C. DUCU3, V. MALINOVSCHI3, X. YANING4, N. ALDEA1,*

Affiliation

  1. National Institute for Research and Development of Isotopic and Molecular Technologies, P. O. Box 700, 400293Cluj- Napoca, Romania
  2. University of Missouri- Columbia, 223 Physics Building, MO 65211, USA
  3. University of Pitesti, Advanced Materials Department, Romania
  4. Coordination Laboratory of National Center for Nanoscience and Nanotechnology, Synchrotron Radiation Facilities of Beijing Electron Positron Collider, People’s Republic of China

Abstract

A series of supported gold catalysts were studied by X-ray diffraction (XRD) in order to determine the Au average particle size, microstrain information and probability of faults. The gold catalysts samples (up to 5 wt.% gold content) were prepared by two methods - impregnation of the oxidic support with aqueous solution of HAuCl4.3H2O and homogeneous deposition precipitation using urea as precipitating agent. The following metal oxides, with high specific surface area were used as supports: Cr2O3, CeO2, TiO2, SiO2, Al2O3 and ZrO2. The XRD method is based on the deconvolution of the experimental Xray line profiles (XRLP) (111), (200), (220) and (311) using Fourier transform procedure. The global structure is determined by fitting the XRLP with the generalized Fermi function. The X-ray diffraction data was collected at room temperature, using Bragg-Brentano (BB) geometry installed on DRON 2 set up, connected with a PC. The samples were next analyzed by extended X-ray absorption fine structure (EXAFS) of the Au LIII-edge using synchrotron radiation in order to determine their local structure that explains the strong deformation of the metal due to its interaction with the oxide supports..

Keywords

Supported gold catalysts, Local and global structure, Metal support interaction, X-ray diffraction, Synchrotron radiation.

Submitted at: Feb. 25, 2008
Accepted at: Aug. 28, 2008

Citation

M. LAZAR, V. ALMASAN, S.PINTEA, B. BARZ, C. DUCU, V. MALINOVSCHI, X. YANING, N. ALDEA, Preparation and structural characterization by XRD and XAS of the supported gold catalysts, Journal of Optoelectronics and Advanced Materials Vol. 10, Iss. 9, pp. 2244-2251 (2008)