Ionic dispersion of Pt over CeO2 by the combustion method: Structural investigation by XRD, TEM, XPS, and EXAFS

Parthasarathi Bera, K. R. Priolkar, Arup Gayen, P. R. Sarode, M. S. Hegde, S. Emura, R. Kumashiro, V. Jayaram, G. N. Subbanna

研究成果: Article査読

283 被引用数 (Scopus)

抄録

The structure and chemical nature of Pt in combustion-synthesized Pt/CeO2 catalysts have been investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), extended X-ray absorption fine structure (EXAFS), and temperature-programmed reaction (TPR). Catalytic oxidation of CO over Pt/CeO2 is correlated with its structure. High-resolution XRD studies show that the structure could be refined for the composition of Ce1-xPtxO2-δ in the fluorite structure with 6% oxide ion vacancy. TEM images show very few Pt particles on the CeO2 crystallite surface in as-prepared samples and a decrease in the density of Pt metal particles is observed on heating. XPS studies demonstrate that Pt is dispersed mostly in +2 (72%) and +4 (21%) oxidation states on CeO2, whereas only 7% is present as Pt metal particles. On heat treatment, Pt2+ species increase at the cost of Pt4+ ions. EXAFS studies show the average coordination number of 1.3 around the platinum ion in the first shell of 1% Pt/CeO2 at a distance of 1.98 Å, indicating oxide ion vacancy around the platinum ion. On heating, the average oxygen coordination of Pt and oxygen increases to 2.3. The second shell at 2.97 Å is due to Pt-Pt coordination, which is absent in PtO2 and PtO. The third shell at 3.28 Å is not observed either in Pt metal or any of the platinum oxides, which could be attributed to Pt2+-Ce4+ correlation. Thus, Pt/CeO2 forms a Ce1-xPtxO2-δ type of solid solution having Pt2+-O-Ce4+- kinds of linkages.

本文言語English
ページ(範囲)2049-2060
ページ数12
ジャーナルChemistry of Materials
15
10
DOI
出版ステータスPublished - 2003 5月 20
外部発表はい

ASJC Scopus subject areas

  • 化学 (全般)
  • 化学工学(全般)
  • 材料化学

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