Adsorption of water on FeO(111) and Fe3O4(111): identification of active sites for dissociation

Abstract

The adsorption of water on epitaxial FeO(111) and Fe3O4(111) films structurally well characterized by STM and LEED was investigated with photoelectron and thermal desorption spectroscopy. On the FeO(111) surface terminated by a close-packed oxygen layer monomeric water species get physisorbed. On the Fe3O4(111) surface terminated by ¼ monolayer of Fe atoms located over a close-packed oxygen layer underneath water dissociates resulting in adsorbed OH groups. The OH saturation coverage corresponds to the number of surface Fe atoms, which is much larger than the surface defect concentrations. Therefore, the dissociation takes place at Fe sites exposed on the regular Fe3O4(111) surface, and the FeO(111) surface is chemically inert because no Fe sites exist thereon.

Molecular scale investigations of the reactivity of magnetite with formic acid, pyridine, and carbon tetrachloride

“…3). This value is also in good agreement with the height of 4.8 Å measured using STM for single crystal Fe 3 O 4 (111), thin film Fe 3 O 4 (111) (Weiss et al, 1993;Kim et al, 1998;Joseph et al, 1999b;Shaikhutdinov et al, 1999Shaikhutdinov et al, , 2000 and reduced a-Fe 2 O 3 (0001) (Fellows et al, 2000).…”

Raman study of magnetite (Fe3O4): laser‐induced thermal effects and oxidation

“…Their inevitable occurrence results from the dissociation of water molecules interacting with the surface of magnetite. 12,13 It was not a purpose of this work to provide a detailed picture of the mechanism of the laser-induced oxidation process of magnetite. We rather aimed at establishing the connections between the laser power, evolution of Raman spectra due to the oxidation, the temperature of the laserilluminated spot and the grain-size effect.…”

Adsorption of water on JSC‐1A (simulated moon dust samples)—a surface science study

“…[19] In contrast, on Fe 3 O 3 (111), which exposes Fe sites, water dissociates. [18] Similarly, for the Al-terminated Al 2 O 3 (0001) surface, dissociation of water is reported but not for O-terminated sapphire films (Ref. 19 and references therein).…”

“…[18] For FeO(111) films, water adsorbs molecularly with well resolved ML/multilayer TDS peaks. Above adsorption temperatures of 120 K, ordered two-dimensional (2D) islands form which completely cover (wet) the surface at saturation.…”