X-ray photoelectron spectroscopic study on the goethites with variations in crystallinity and morphology: their effects on surface hydroxyl concentration

Autor: Seiko Nemoto, Tamao Hatta, Takuya Echigo, Shigeru Takizawa
Rok vydání: 2012
Předmět:
Zdroj: Physics and Chemistry of Minerals. 39:769-778
ISSN: 1432-2021
0342-1791
DOI: 10.1007/s00269-012-0531-y
Popis: We examined the effects of crystallinity and crystal morphology on surface hydroxyl concentration of goethite using four kinds of goethite samples prepared by aging a hydrous ferric oxide (ferrihydrite) at different temperatures ranging from 4 to 70 °C. These samples were analyzed with the following methods: powder X-ray diffraction, Brunauer–Emmett–Teller surface area analyzer, atomic force microscopy, attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and high-resolution X-ray photoelectron spectroscopy (XPS). The first three analyses showed that the goethite aged at lower temperature has lower crystallinity, smaller particle size and lower aspect ratio. The ATR-FTIR analysis revealed that the OH-stretching band of goethite aged at 4 °C moves to slightly higher wavenumber than those of the samples aged at higher temperatures. Their XPS analyses demonstrated that variation in the concentration of surface hydroxyl group ranges from 6.6 (nm−2) for the sample aged at 4 °C to 7.7 (nm−2) for the sample aged at 70 °C. Considering the analytical depth of the XPS (~5 nm), photoelectrons are emitted from the uppermost layers of the analyte. Hence, XPS results are interpreted to reflect variations in the morphology of fine crystals (
Databáze: OpenAIRE
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