Authors
Frances E Zengotita, Nabajit Lahiri, Mark H Engelhard, Maksym Zhukovskyi, Manuel R Vejar, Kevin M Rosso, Carolyn I Pearce, Amy E Hixon
Published in
The journal of physical chemistry. C, Nanomaterials and interfaces. Volume 129. Issue 15. Pages 7316-7326. Apr 17, 2025. Epub Apr 07, 2025.
Abstract
Nanoscale iron oxides (e.g., hematite (α-Fe2O3)) have unique properties, such as enhanced chemical reactivity and high surface area, when compared with their bulk counterparts. These nanoscale surfaces can be more reactive due to the presence of defects (e.g., oxygen vacancies). In this work, we probed the surface chemistry of bulk and nanoscale hematite via X-ray photoelectron spectroscopy, electron microscopy, and powder X-ray diffraction. Oxygen exposure and vacuum annealing experiments were conducted to add or remove oxygen vacancies and remove adventitious carbon. In the absence of the oxygen annealing step, vacuum annealing resulted in partial reduction of Fe(III) to Fe(II) on all hematite surfaces. This is a size-dependent effect, with the extent of reduction increasing as the crystallite size decreases. In addition, the atomic concentrations of carbon increased on all iron oxide surfaces after vacuum annealing. Oxygen annealing almost completely removed carbon from sample surfaces, and no Fe(III) reduction was observed in the absence of carbon. Under these conditions, the results reveal that carbonaceous material enhances oxygen vacancy formation, which then facilitates the reduction of Fe(III) on hematite surfaces. We provide new insights into the mechanisms of Fe(III) reduction on both bulk and nanoscale hematite surfaces and establish the major role of carbon in oxygen vacancy formation.
PMID:
40265133
Bibliographic data and abstract were imported from PubMed on 23 Apr 2025.
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