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X‐ray Photoelectron Spectroscopy as a Tool to Differentiate Silicon‐Bonding State in Amorphous Iron Oxides
Author(s) -
Vempati R. K.,
Loeppert R. H.,
Dufner D. C.,
Cocke D. L.
Publication year - 1990
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1990.03615995005400030010x
Subject(s) - ferrihydrite , x ray photoelectron spectroscopy , silicate , biotite , silicon , analytical chemistry (journal) , amorphous solid , materials science , binding energy , oxidation state , crystallography , chemistry , adsorption , metal , nuclear magnetic resonance , physics , quartz , organic chemistry , chromatography , metallurgy , composite material , nuclear physics
An x‐ray photoelectron spectroscopy (XPS) study was conducted to: (i) compare the Si (2 p ) and O (1 s ) peaks of selected Si‐containing minerals, and (ii) evaluate the application of XPS in identifying probable Si‐bonding environments in Si‐containing ferrihydrites. For silica gel, the Si (2 p ) and O (1 s ) XPS peaks occurred at 104.0 and 534.2 eV, respectively; with biotite, these peaks occurred at 102.8 and 532.4 eV. The difference in the Si (2 p ) binding energies between silica gel and biotite was attributed to differences in the Si‐bonding environment and the number of ‐Si‐O‐Si‐ linkages at corners of the SiO 4 tetrahedron, and the charge deficit in the tetrahedral layer of biotite. The Si (2 p ) XPS peak for silicate adsorbed on ferrihydrite occurred at 100.9 eV, which indicated the probable presence of ligand‐bound silicate or small units of polymerized silica at the ferrihydrite surface. For ferrihydrite samples treated with an excess of Si (≥75 g kg −1 ), peaks attributable to a separate Si‐rich phase were identified on decomposition of the Si (2 p ) and O (1 s ) XPS peaks. In the case of ferrihydrite coprecipitated with silicate at Si/Fe molar ratios ≥0.10, the Si (2 p ) peak occurred at approximately 102.8 eV, which is a position similar to that observed for layer silicates, indicating the possible presence of Si, i.e., the presence of ‐Fe‐O‐Sl‐ bonds, within the ferrihydrite structure.