Dresden 2014 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 58: Oxide and Insulator Surfaces II
O 58.9: Vortrag
Mittwoch, 2. April 2014, 18:00–18:15, PHY C 213
Tuning the electronic structure of Fe3O4 by adsorbates: A DFT+U investigation — •Narasimham Mulakaluri1 and Rossitza Pentcheva2 — 1Fraunhofer Institute for Mechanics of Materials, Freiburg, Germany — 2Dept. for Earth and Environmental Sciences, University of Munich,Germany
Fe3O4 plays an important role in many technologically relevant catalytic reactions such as HT-WGS (high temperature water gas phase shift reaction). To tune the catalytic activity it is important to understand and selectively modify the surface electronic structure. Using density functional theory together with an on-site Coulomb repulsion term (GGA+U), we explore the progressive reduction of the Fe3O4(001) surface by additional deposition of Fe [1] or hydrogen [2]. The thermodynamic stability of different terminations reveals that additional Fe atoms switch to surface octahedral sites instead of the bulk structure continuation at tetrahedral sites (A) on top of the B-termination (containing oxygen and octahderal iron). With increasing coverage an antiferromagnetic and strongly buckled FeO layer is formed on top of the Fe3O4(001) surface. The deposition of Fe leads to a progressive reduction of Fe in the surface and subsurface layers to Fe2+ and thus allows control of the Fe2+/Fe3+ ratio and the redox activity at the Fe3O4(001) surface. The enhancement of Fe2+ in the near surface region is also supported by XPS experiments [1]. Parallels to hydrogen and metal adsorption are also discussed.
[1] Z. Novotny, N. Mulakaluri et.al, Phys. Rev. B 87, 195410 (2013).
[2] N. Mulakaluri, R. Pentcheva, J. Phys. Chem. C 116, 16447 (2012).