| AVS 64th International Symposium & Exhibition | |
| Surface Science Division | Thursday Sessions |
| Session SS+EM+HC+MI-ThM |
| Session: | Oxides: Structures and Reactions |
| Presenter: | Gareth Parkinson, TU Wien, Austria |
| Authors: | G.S. Parkinson, TU Wien, Austria F. Kraushofer, TU Wien, Austria Z. Jakub, TU Wien, Austria M. Bichler, TU Wien, Austria J. Hulva, TU Wien, Austria M. Schmid, TU Wien, Austria U. Diebold, TU Wien, Austria P. Blaha, TU Wien, Austria |
| Correspondent: | Click to Email |
Hematite (α-Fe2O3) is a promising material for technological applications due to its abundance, low cost and chemical stability. Its 2.2 eV bandgap makes it potentially ideal as a photoanode for photoelectrochemical water splitting, [1] but performance is hampered by slow reaction kinetics and the need for a significant overpotential. Little is known about the atomic-scale structure of hematite surfaces, and even less about how this relates to photocatalytic activity.
To date, most surface science studies of α-Fe2O3 have focused on the (001) facet, but preparing a stoichiometric surface under UHV conditions has proven problematic. Some authors have investigated the equally relevant (012) surface, [2][3][4] and reported that a (1x1) and a reduced (2x1) termination can be reversibly prepared. Several models have been proposed for the (2x1) reconstruction, but as yet no scanning probe data exists to support or refute them.
Here we present a multi-technique study of the (1x1) and (2x1) surfaces of α-Fe2O3 (012), as well as their interaction with water. The data acquired for the (1x1) termination support a bulk termination model, as predicted by previous publications, but STM and nc-AFM images of the (2x1) reconstruction are inconsistent with previously proposed models. [3] We propose a new model based on ordered oxygen vacancies, the plausibility of which is confirmed by density functional theory (DFT) results. TPD and XPS data reveal that the (1x1) surface adsorbs water in a mixed-mode fashion, whereas the interaction with the (2x1) surface is entirely dissociative. We propose models for the structure of the adsorbed overlayers based on scanning probe microscopy data.
References
[1] Parkinson, G. S. Surface Science Reports 71, 272-365 (2016).
[2] Henderson, M. A., Joyce, S. A. & Rustad, J. R. Surface Science 417, 66-81 (1998).
[3] Henderson, M. A. Surface science 515, 253-262 (2002).
[4] Gautier-Soyer, M., Pollak, M., Henriot, M. & Guittet, M. Surface science 352, 112-116 (1996).