Surface reduction state determines stabilization and incorporation of Rh on α-Fe2O3(1 -1 0 2)

F. Kraushofer, N. Resch, M. Eder, A. Rafsanjani-Abbasi, S. Tobisch, Z. Jakub, G. Franceschi, M. Riva, M. Meier, M. Schmid, U. Diebold, G. S. Parkinson

Institut für Angewandte Physik, TU Wien, 1040 Wien, Austria
Department of Chemistry & Catalysis Research Center, TU München, 85748 Garching, Germany
Faculty of Physics and Center for Computational Materials Science, University of Vienna, 1090 Wien, Austria

Adv. Mater. Interfaces 8 (2021) 2001908

Iron oxides (FeOx) are among the most common support materials utilized in single atom catalysis. The support is nominally Fe2O3, but strongly reductive treatments are usually applied to activate the as-synthesized catalyst prior to use. Here, Rh adsorption and incorporation on the (1 -1 0 2) surface of hematite (α-Fe2O3) are studied, which switches from a stoichiometric (1 × 1) termination to a reduced (2 × 1) reconstruction in reducing conditions. Rh atoms form clusters at room temperature on both surface terminations, but Rh atoms incorporate into the support lattice as isolated atoms upon annealing above 400 °C. Under mildly oxidizing conditions, the incorporation process is so strongly favored that even large Rh clusters containing hundreds of atoms dissolve into the surface. Based on a combination of low-energy ion scattering (LEIS), X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM) data, as well as density functional theory (DFT), it is concluded that the Rh atoms are stabilized in the immediate subsurface, rather than the surface layer.

Corresponding author: Gareth Parkinson (parkinson at iap_tuwien_ac_at).

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