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Structure and reactivity of the hydrated hematite (0 0 0 1) surface |
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| Authors: | Thomas P. Trainor Anne M. Chaka Peter J. Eng Glenn A. Waychunas Gordon E. Brown Jr. |
| Affiliation: | a Department of Chemistry and Biochemistry, University of Alaska Fairbanks, P.O. Box 756160, Fairbanks, AK 99775, USA b National Institute of Standards and Technology, Gaithersburg, MD 20899, USA c Consortium for Advanced Radiation Sources, University of Chicago, Chicago, IL 60637, USA d Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA e Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305, USA f Stanford Synchrotron Radiation Laboratory, SLAC, 2575 Sand Hill Road, MS 69, Menlo Park, CA 94025, USA |
| Abstract: | The structure of the hydroxylated hematite (0 0 0 1) surface was investigated using crystal truncation rod diffraction and density functional theory. The combined experimental and theoretical results suggest that the surface is dominated by two hydroxyl moieties—hydroxyls that are singly coordinated and doubly coordinated with Fe. The results are consistent with the formation of distinct domains of these surface species; one corresponding to the hydroxylation of the surface Fe-cation predicted to be most stable under UHV conditions, and the second a complete removal of this surface Fe species leaving the hydroxylated oxygen layer. Furthermore, our results indicate that the hydroxylated hematite surface structures are significantly more stable than their dehydroxylated counterparts at high water partial pressures, and this transition in stability occurs at water pressures orders of magnitude below the same transition for α-alumina. These results explain the observed differences in reactivity of hematite and alumina (0 0 0 1) surfaces with respect to water and binding of aqueous metal cations. |
| Keywords: | Iron oxide Density functional calculations Surface structure, morphology, roughness, and topography |
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