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Surface potential at the hematite (001) crystal plane in aqueous environments and the effects of prolonged aging in water

Lützenkirchen, Johannes ORCID iD icon 1; Preočanin, Tajana; Stipić, Filip; Heberling, Frank ORCID iD icon 1; Rosenqvist, Jörgen; Kallay, Nikola
1 Institut für Nukleare Entsorgung (INE), Karlsruher Institut für Technologie (KIT)

Abstract (englisch):

The surface potentials of a (0 0 1) terminated hematite crystal that was annealed at high-temperature were measured as a function of pH by means of the corresponding single crystal electrode. The surface potential at a given pH did not depend on the electrolyte concentration, and was found to exhibit an inflection point. The shape of the function is in phenomenological agreement with the presence of two distinct surface terminations (O and Fe) that have been previously reported for this surface. Aging of the annealed hematite surface, in aqueous electrolyte medium over 2 weeks, leads to a drastic change in the surface potential pH curve. The surface potential becomes that of the ideal O termination. While the O termination data can be modeled using the MUSIC approach, the initial sample that is expected to correspond to the two-domain surface with O and Fe terminations cannot be described within the MUSIC approach based on previously published surface diffraction data. However, the experimental data fall between the O and Fe termination limiting cases when the point of zero potential is placed at the inflection point. The fact that a surface with the two terminations cannot be modeled may be attributed to various issues, three of which are discussed: (i) the general difficulty to average the potential arising from both terminations, which furthermore are short-circuited via the crystal, (ii) the difficulty of treating patchwise heterogeneous surfaces in surface complexation models, and (iii) the incapability of surface complexation models in their present form to describe potential gradients within the solid. ... mehr

DOI: 10.1016/j.gca.2013.06.042
Zitationen: 23
Web of Science
Zitationen: 22
Zitationen: 22
Zugehörige Institution(en) am KIT Institut für Nukleare Entsorgung (INE)
Publikationstyp Zeitschriftenaufsatz
Publikationsjahr 2013
Sprache Englisch
Identifikator ISSN: 0016-7037, 1872-9533
KITopen-ID: 1000068766
Erschienen in Geochimica et cosmochimica acta
Verlag Elsevier
Band 120
Heft Nov
Seiten 479-486
Nachgewiesen in Scopus
Web of Science
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