[Zurück]

F. Kraushofer, F. Mirabella, J. Xu, J. Pavelec, J. Balajka, M. Müllner, N. Resch, Z. Jakub, J. Hulva, M. Meier, M. Schmid, U. Diebold, G. Parkinson:
"Self-limited growth of an oxyhydroxide phase at the Fe3O4(001) surface in liquid and ambient pressure water";
Journal of Chemical Physics, 151 (2019), S. 1547021 - 1547028.

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
ultrahigh vacuum-compatible dosing of liquids to explore the stability of the Fe3O4(001)-(
√
2 ×
√
2)R45○ surface following exposure to liquid
and ambient pressure water. X-ray photoelectron spectroscopy and low-energy electron diffraction data show that extensive hydroxylation
causes the surface to revert to a bulklike (1 × 1) termination. However, scanning tunneling microscopy (STM) images reveal a more complex
situation, 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. The resemblance of the STM
images to those acquired in previous electrochemical STM studies leads us to believe that a similar structure exists at the solid-electrolyte
interface during immersion at pH 7.

http://dx.doi.org/10.1063/1.5116652