| AVS 66th International Symposium & Exhibition | |
| Fundamental Aspects of Material Degradation Focus Topic | Thursday Sessions |
| Session DM2+BI+SS-ThA |
| Session: | Fundamentals of Catalyst Degradation: Dissolution, Oxidation and Sintering |
| Presenter: | Florian Kraushofer, TU Wien, Austria |
| Authors: | F. Kraushofer, TU Wien, Austria F. Mirabella, TU Wien, Austria, Germany J. Xu, TU Wien, Austria J. Pavelec, TU Wien, Austria J. Balajka, TU Wien, Austria M. Müllner, TU Wien, Austria N. Resch, TU Wien, Austria Z. Jakub, TU Wien, Austria J. Hulva, TU Wien, Austria M. Meier, TU Wien, Austria M. Schmid, TU Wien, Austria U. Diebold, TU Wien, Austria G.S. Parkinson, TU Wien, Austria |
| Correspondent: | Click to Email |
Atomic-scale investigations of metal oxide surfaces exposed to aqueous environments are vital to understand degradation phenomena (e.g. dissolution and corrosion) as well as the performance of these materials in applications. Here, we utilize a new experimental setup for the UHV-compatible dosing of liquids to explore the stability of the Fe3O4(001)-(√2 × √2)R45° surface following exposure to liquid and ambient pressure water, using low energy electron diffraction (LEED), x-ray photoemission spectroscopy (XPS) and scanning tunnelling microscopy (STM).
Short-time exposure of the surface to clean H2O results in hydroxylation of the surface, which is not observed in UHV. After longer exposure times, we observe lifting of the (√2 × √2)R45° reconstruction with LEED and stronger hydroxylation of the surface with XPS, in agreement with previous reports. However, scanning tunnelling microscopy (STM) images reveal a more complex situation than simply reverting to a bulk-truncation, with the slow growth of an oxyhydroxide phase, which ultimately saturates at approximately 40% coverage. We conclude that the new material contains OH groups from dissociated water coordinated to Fe cations extracted from subsurface layers, and that the surface passivates once the surface oxygen lattice is saturated with H because no further dissociation can take place.