Dresden 2017 – scientific programme

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O: Fachverband Oberflächenphysik

O 81: Oxide and Insulator Surfaces: Adsorption II

O 81.9: Talk

Wednesday, March 22, 2017, 18:00–18:15, WIL C107

Water adsorption on top of the hematite(0001) surface at medium and high coverage regimes — •Roman Ovcharenko and Elena Voloshina — Institut für Chemie, Humboldt-Universität zu Berlin, Berlin, Germany

On the pristine hematite(0001) half-iron termination isolated water molecules form an dissociated structure with an OH group attached to a surface iron ion and a protonated surface oxygen ion [1]. At increasing water loading the water-water interaction starts to play a crucial role in the adsorption behaviour and energetics. Thus, according to our PBE+U+D2 calculations, for the 1/2 monolayer (ML) coverage fully dissociated and mixed adsorption structures are energetically degenerated. Nevertheless, both water molecules and OH-groups adsorb at different coordinatively unsaturated metal sites and do not tend to form a dimer structure as it was found for the magnetite(111) surface [2]. When increasing water loading further up to 3/4 ML, a tendency to form mixed adsorption structures become even more pronounced. This is different to water adsorption on top of the isomorphic corundum (0001) surface, where by increasing water loading each following molecule was found to dissociatively adsorb at new metal site up to the full monolayer. Thus, the hematite(0001) surface, partially inheriting the properties of both magnetite and aluminium oxide, demonstrates unique chemical reactivity towards water adsorption at medium and high coverage regimes. [1] R. Ovcharenko et al., Phys. Chem. Chem. Phys. 18, 25560 (2016) [2] X. Li et al., J. Phys. Chem. C 120, 1056 (2015)