Structure, Magnetism, and the Interaction of Water with Ti-Doped Fe3O4 Surfaces
| Autor: | Kevin M. Rosso, Carolyn I. Pearce, Elke Arenholz, Kelsey A. Stoerzinger, Timothy C. Droubay, Zhi Liu, Vaithiyalingam Shutthanandan |
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| Rok vydání: | 2019 |
| Předmět: |
Materials science
Magnetic circular dichroism Magnetism Analytical chemistry 02 engineering and technology Surfaces and Interfaces 010402 general chemistry 021001 nanoscience & nanotechnology Condensed Matter Physics 01 natural sciences Surface energy 0104 chemical sciences Pulsed laser deposition chemistry.chemical_compound Adsorption X-ray photoelectron spectroscopy chemistry Electrochemistry General Materials Science 0210 nano-technology Spectroscopy Stoichiometry Magnetite |
| Zdroj: | Langmuir. 35:13872-13879 |
| ISSN: | 1520-5827 0743-7463 |
| DOI: | 10.1021/acs.langmuir.9b02468 |
| Popis: | The functionality of magnetite, Fe3O4, for catalysis and spintronics applications is dependent on the molar ratio of Fe2+ and Fe3+ and their distribution at the surface. In turn, this depends on a poorly understood interplay between crystallographic orientation, dopants, and the reactive adsorption of atmospheric species such as water. Here, (100)-, (110)-, and (111)-oriented films of titanomagnetite, Fe(3-x)TixO4, were grown by pulsed laser deposition and their composition, valence distribution, magnetism, and interaction with water were studied by ambient pressure X-ray photoelectron spectroscopy (AP-XPS) and X-ray magnetic circular dichroism. Although the bulk compositions match the desired stoichiometry, the surfaces were found to be enriched in Ti4+, especially the top 1 nm. The highest surface energy (110) film was the most reduced, tied to local Ti enrichment, and a corresponding decreased magnetic moment. AP-XPS showed that incorporation of x = 0.25 Ti dramatically lowered the propensity to form hydroxyl species at a given relative humidity, and also that hydroxylation is relatively invariant with orientation. In contrast, the affinity for water is similar across orientations, regardless of Ti incorporation, suggesting that relative humidity controls its uptake. The findings may help demystify the interactions that lead to specific distributions of Fe2+ and Fe3+ at magnetite surfaces, toward design of more deliberately active catalysts and magnetic devices. |
| Databáze: | OpenAIRE |
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