The reactivity of magnetite in the environment and in catalysis is dependent on the molar ratio of Fe2+ and Fe3+ at the surface. This in turn depends on poorly understood relationships between crystallographic orientation, dopants, and the reactive adsorption of water. Here we report a detailed study of the composition, valence distribution, and magnetism of epitaxially grown Fe(3−x)TixO4 thin films and their interaction with water using APXPS and XMCD. Surfaces tended to be enriched in Ti4+ relative to their bulk composition, especially the top 1 nm. The highest surface energy (110) film was the most reduced, and showed a decreased magnetic moment. Incorporation of x = 0.25 dramatically lowered the propensity to form hydroxyl species at a given relative humidity. In contrast, the affinity for water was similar across orientations, suggesting that relative humidity controls water uptake. The findings help explain the interactions that lead to specific distributions of Fe2+ and Fe3+ at magnetite surfaces, toward an improved understanding of its redox functionality.

Structure, magnetism, and the interaction of water with Ti-doped Fe3O4 surfaces

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.