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Title: Surface diffraction study of the hydrated hematite (1102) surface.

Abstract

The structure of the hydroxylated {alpha}-Fe{sub 2}O{sub 3(1{bar 1}02)} surface prepared via a wet chemical and mechanical polishing (CMP) procedure was determined using X-ray crystal truncation rod diffraction. The experimentally determined surface model was compared with theoretical structures developed from density functional theory (DFT) calculations to identify the most likely protonation states of the surface (hydr)oxo moieties. The results show that the hydroxylated CMP-prepared surface differs from an ideal stoichiometric termination due to vacancies of the near surface bulk Fe sites. This result differs from previous ultra high vacuum studies where two stable terminations were observed: a stoichiometric (1 x 1) termination and a partially reduced (2 x 1) reconstructed surface. The complementary DFT studies suggest that hydroxylated surfaces are thermodynamically more stable than dehydroxylated surfaces in the presence of water. The results illustrate that the best fit surface model has predominantly three types of (hydr)oxo functional groups exposed at the surface at circumneutral pH: Fe-OH{sub 2}, Fe{sub 2}-OH, and Fe{sub 3}-O and provide a structural basis for interpreting the reactivity of model iron-(hydr)oxide surfaces under aqueous conditions.

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC); National Science Foundation (NSF)
OSTI Identifier:
962546
Report Number(s):
ANL/XSD/JA-58085
Journal ID: ISSN 0039-6028; SUSCAS; TRN: US200916%%21
DOE Contract Number:
DE-AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Surf. Sci.; Journal Volume: 601; Journal Issue: 2007
Country of Publication:
United States
Language:
ENGLISH
Subject:
36 MATERIALS SCIENCE; X-RAY DIFFRACTION; DENSITY FUNCTIONAL METHOD; HEMATITE; SURFACE PROPERTIES; VACANCIES

Citation Formats

Tanwar, K. S., Lo, C. S., Eng, P. J., Catalano, J. G., Walko, D. A., Brown, G. E., Jr., Waychunas, G. A., Chaka, A. M., Trainor, T. P., X-Ray Science Division, Univ. of Alaska Fairbanks, NIST, Univ. of Chicago, Stanford Univ., LBNL, and SSRL. Surface diffraction study of the hydrated hematite (1102) surface.. United States: N. p., 2007. Web. doi:10.1016/j.susc.2006.10.021.
Tanwar, K. S., Lo, C. S., Eng, P. J., Catalano, J. G., Walko, D. A., Brown, G. E., Jr., Waychunas, G. A., Chaka, A. M., Trainor, T. P., X-Ray Science Division, Univ. of Alaska Fairbanks, NIST, Univ. of Chicago, Stanford Univ., LBNL, & SSRL. Surface diffraction study of the hydrated hematite (1102) surface.. United States. doi:10.1016/j.susc.2006.10.021.
Tanwar, K. S., Lo, C. S., Eng, P. J., Catalano, J. G., Walko, D. A., Brown, G. E., Jr., Waychunas, G. A., Chaka, A. M., Trainor, T. P., X-Ray Science Division, Univ. of Alaska Fairbanks, NIST, Univ. of Chicago, Stanford Univ., LBNL, and SSRL. Mon . "Surface diffraction study of the hydrated hematite (1102) surface.". United States. doi:10.1016/j.susc.2006.10.021.
@article{osti_962546,
title = {Surface diffraction study of the hydrated hematite (1102) surface.},
author = {Tanwar, K. S. and Lo, C. S. and Eng, P. J. and Catalano, J. G. and Walko, D. A. and Brown, G. E., Jr. and Waychunas, G. A. and Chaka, A. M. and Trainor, T. P. and X-Ray Science Division and Univ. of Alaska Fairbanks and NIST and Univ. of Chicago and Stanford Univ. and LBNL and SSRL},
abstractNote = {The structure of the hydroxylated {alpha}-Fe{sub 2}O{sub 3(1{bar 1}02)} surface prepared via a wet chemical and mechanical polishing (CMP) procedure was determined using X-ray crystal truncation rod diffraction. The experimentally determined surface model was compared with theoretical structures developed from density functional theory (DFT) calculations to identify the most likely protonation states of the surface (hydr)oxo moieties. The results show that the hydroxylated CMP-prepared surface differs from an ideal stoichiometric termination due to vacancies of the near surface bulk Fe sites. This result differs from previous ultra high vacuum studies where two stable terminations were observed: a stoichiometric (1 x 1) termination and a partially reduced (2 x 1) reconstructed surface. The complementary DFT studies suggest that hydroxylated surfaces are thermodynamically more stable than dehydroxylated surfaces in the presence of water. The results illustrate that the best fit surface model has predominantly three types of (hydr)oxo functional groups exposed at the surface at circumneutral pH: Fe-OH{sub 2}, Fe{sub 2}-OH, and Fe{sub 3}-O and provide a structural basis for interpreting the reactivity of model iron-(hydr)oxide surfaces under aqueous conditions.},
doi = {10.1016/j.susc.2006.10.021},
journal = {Surf. Sci.},
number = 2007,
volume = 601,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}