Self-limited growth of an oxyhydroxide phase at the Fe3O4(001) surface in liquid and ambient pressure water

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. S. Parkinson

Institut für Angewandte Physik, TU Wien, 1040 Wien, Austria
Department of Metallurgical Engineering, College of Materials Science and Engineering, Chongqing University, Shapingba District, Chongqing 400044, China

J. Chem. Phys. 151 (2019) 154702

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.

Corresponding author: Gareth S. Parkinson (parkinson at iap_tuwien_ac_at).

This article was featured in a SCIlight: "Rusting at the atomic level" by Stacy W. Kish.

Users with online access to The Journal of Chemical Physics can load the article from the publisher.
A preprint is available at