Polarized total-reflection fluorescence EXAFS study of anisotropic structure analysis of Co oxides on [alpha]-Al[sub 2]O[sub 3] (0001) as model surfaces for active oxidation catalysts

Journal Article · Sat Jan 01 00:00:00 EST 1994 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1006/jcat.1994.1018· OSTI ID:7036613

Shirai, Masayuki; Inoue, Tomoya; Onishi, Hiroshi; Asakura, Kiyotaka; Iwasawa, Yasuhiro ^[1]

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1. Univ. of Tokyo (Japan)

An in situ Polarized Total-Reflection Fluorescence Extended X-ray Absorption Fine Structure (PTRF-EXAFS) technique was developed to analyze anisotropic structures of metal sites on surfaces. The PTRF-EXAFS can provide structural information in two different directions, separately, parallel (s-polarization) and normal (p-polarization) to the support surface. This technique was used to analyze the anisotropic structures of two kinds of Co-oxides on [alpha]-Al[sub 2]O[sub 3] (0001) which were derived from Co[sub 2](CO)[sub 8] and model surfaces of Co-oxide catalysts supported on [alpha]-Al[sub 2]O[sub 3] active for CO oxidation. The s- and p-polarized EXAFS analysis revealed that after contact of Co[sub 2](CO)[sub 8] with [alpha]-Al[sub 2]O[sub 3] (0001), followed by oxidation with O[sub 2] at 300 K, Co atoms occupied the threefold hollow sites of [alpha]-Al[sub 2]O[sub 3] (0001) as monomers (Co-C = 0.208 nm). By oxidation at 873 K, the Co monomers aggregated to form small spinel-like particles [Co[sub 3]O[sub 4]][sub n] with ca. 0.9 nm dimension. The anisotropic structure analysis shows that the particles of seven layers grew with the spinel (001) plane parallel to the [alpha]-Al[sub 2]O[sub 3] (0001) plane. 20 refs., 11 figs., 4 tabs.

• OSTI ID: 7036613
• Journal Information: Journal of Catalysis; (United States), Vol. 145:1; ISSN 0021-9517
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
01 COAL, LIGNITE, AND PEAT
COBALT OXIDES
FLUORESCENCE SPECTROSCOPY
X-RAY SPECTROSCOPY
CATALYST SUPPORTS
CHALCOGENIDES
COBALT COMPOUNDS
EMISSION SPECTROSCOPY
OXIDES
OXYGEN COMPOUNDS
SPECTROSCOPY
TRANSITION ELEMENT COMPOUNDS
400201* - Chemical & Physicochemical Properties
010408 - Coal
Lignite
& Peat- C1 Processes- (1987-)