Crystallite Size and Morphology of the Phases in Au/TiO2 and Au/Ce-TiO2 Catalysts
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- 作者：Xim Bokhimi ; Rodolfo Zanella
- 刊名：Journal of Physical Chemistry C
- 出版年：2007
- 出版时间：February 15, 2007
- 年：2007
- 卷：111
- 期：6
- 页码：2525 - 2532
- 全文大小：537K
- 年卷期：v.111,no.6(February 15, 2007)
- ISSN：1932-7455
文摘
Au/TiO2 and Au/Ce-TiO2 catalysts with 5 wt % Au and 12 wt % cerium were prepared with the sol geltechnique, and characterized using X-ray powder diffraction and transmission electron microscopy. Thecrystallography, crystallite size, and morphology of all of the phases in the catalysts, including the metallicgold phase, were obtained by refining the crystalline structures with the Rietveld method. The gold crystallitesize and morphology, which was based on truncated cuboctahedra, depended on the titania polymorph usedas the support: when the support was anatase the gold crystallites had their smallest dimension (1 nm)perpendicular to the (111) planes of gold's crystalline structure, whereas for brookite and rutile this dimension(1.73 for brookite and 1.54 for rutile) was perpendicular to the (200) planes. The large amount of structuraldefects of the support served as particle pinning centers of the gold crystallites, hindering the diffusion thatproduces larger crystallites. From the refinement, the contribution of the metallic gold to the X-ray diffractionpattern of the catalyst was extracted. Cerium doping decreased anatase and brookite crystallite size and increasedthe number of structural defects because cerium atoms incorporated into their crystalline structures.