| AVS 58th Annual International Symposium and Exhibition | |
| Surface Science Division | Thursday Sessions |
| Session SS-ThM |
| Session: | Oxide Surface Structure & Reactivity |
| Presenter: | Kristoffer Meinander, Aarhus U., Denmark |
| Authors: | M.K. Rasmussen, Aarhus U., Denmark K. Meinander, Aarhus U., Denmark A.S. Foster, Tampere Univ. of Tech., Finland B. Hinnemann, Haldor Topsøe A/S, Denmark F.F. Canova, Tampere Univ. of Tech., Finland S. Helveg, Haldor Topsøe A/S, Denmark N.M. Martin, Lund U., Sweden J. Knudsen, Lund U., Sweden A. Vlad, Max-Planck-Institut für Metallforschung, Germany E. Lundgren, Lund U., Sweden A. Stierle, Max-Planck-Institut für Metallforschung, Germany F. Besenbacher, Aarhus U., Denmark J.V. Lauritsen, Aarhus U., Denmark |
| Correspondent: | Click to Email |
Metal oxide spinels are an important class of materials in both ceramics technology and materials science. Although the prototypical ternary metal oxide spinel, magnesium aluminate spinel (MgAl2O4), is widely used, for instance, as a membrane in solid oxide fuel cells and in heterogeneous catalysis, either as a support for active metal nanoclusters or as a catalyst in its own right [1], many of the intricate details of its surface structure still remain unresolved. The atomic-scale surface characterization of similar spinel-type metal oxides has generally been challenging, due to the insulating nature of these materials, a property which limits the use of many standard surface science techniques.
Using a combination of non-contact atomic force microscopy (NC-AFM) and surface X-ray diffraction (SXRD), coupled together with density functional theory (DFT) structure calculations and NC-AFM simulations based on DFT, we have unraveled the complex structure of the polar MgAl2O4 (100) surface. Surprisingly, we find that the surface is terminated by an Al and O-rich structure, with a thermodynamically favored amount of Al atoms interchanged with Mg. These cation antisites, which are low-density defects in the bulk, may be a key element in determining the substrate properties of MgAl2O4, among others its basicity and the likelihood for formation of OH-groups, which are believed to be anchoring sites for metallic nanoclusters, such as Ni, commonly used in steam reforming catalysts.
[1] J. R. Rostrup-Nielsen, J. Sehested, and J. K. Nørskov, Adv. Catal. 47, 65 (2002).