Quality or Quantity? How Structural Parameters Affect Catalytic Activity of Iron Oxides for CO Oxidation

Catalysts, vol. 12, pp. 675

Abstract

The replacement of noble metal catalysts by abundant iron as an active compound in CO oxidation is of ecologic and economic interest. However, improvement of their catalytic performance to the same level as state-of-the-art noble metal catalysts requires an in depth understanding of their working principle on an atomic level. As a contribution to this aim, a series of iron oxide catalysts with varying Fe loadings from 1 to 20 wt% immobilized on a γ-Al2O3 support is presented here, and a multidimensional structure–activity correlation is established. The CO oxidation activity is correlated to structural details obtained by various spectroscopic, diffraction, and microscopic methods, such as PXRD, PDF analysis, DRUVS, Mössbauer spectroscopy, STEM-EDX, and XAS. Low Fe loadings lead to less agglomerated but high percentual amounts of isolated, tetrahedrally coordinated iron oxide species, while the absolute amount of isolated species reaches its maximum at high Fe loadings. Consequently, the highest CO oxidation activity in terms of turnover frequencies can be correlated to small, finely dispersed iron oxide species with a large amount of tetrahedrally oxygen coordinated iron sites, while the overall amount of isolated iron oxide species correlates with a lower light-off temperature.

Authors 11

1. Steffen Schlicher

   Paderborn University

   Affiliation as printed

   Department of Chemistry and Center for Sustainable Systems Design (CSSD), Paderborn University, Warburger Straße 100, 33098 Paderborn, Germany

2. Nils Prinz Aachen Institute of Crystallography

   RWTH Aachen University

   Affiliation as printed

   Institute of Crystallography, RWTH Aachen University, Jägerstr. 17-19, 52066 Aachen, Germany

3. Julius Bürger

   Paderborn University

   Affiliation as printed

   Department of Physics, Paderborn University, Warburger Straße 100, 33098 Paderborn, Germany

4. Andreas Omlor

   University of Kaiserslautern

   Affiliation as printed

   Department of Physics, Technical University of Kaiserslautern, Erwin-Schrödinger-Straße 46, 67663 Kaiserslautern, Germany

5. Christian Singer

   TU Bergakademie Freiberg

   Affiliation as printed

   Institute of Energy Process Engineering and Chemical Engineering, Chair of Reaction Engineering, Technical University of Freiberg, Fuchsmühlenweg 9, 09599 Freiberg, Germany

6. Mirijam Zobel Aachen Institute of Crystallography

   RWTH Aachen University

   Affiliation as printed

   Institute of Crystallography, RWTH Aachen University, Jägerstr. 17-19, 52066 Aachen, Germany

7. Roland Schoch

   Paderborn University

   Affiliation as printed

   Department of Chemistry and Center for Sustainable Systems Design (CSSD), Paderborn University, Warburger Straße 100, 33098 Paderborn, Germany

8. Jörg K. N. Lindner

   Paderborn University

   Affiliation as printed

   Department of Physics, Paderborn University, Warburger Straße 100, 33098 Paderborn, Germany

9. Volker Schünemann

   University of Kaiserslautern

   Affiliation as printed

   Department of Physics, Technical University of Kaiserslautern, Erwin-Schrödinger-Straße 46, 67663 Kaiserslautern, Germany

10. Sven Kureti

    TU Bergakademie Freiberg

    Affiliation as printed

    Institute of Energy Process Engineering and Chemical Engineering, Chair of Reaction Engineering, Technical University of Freiberg, Fuchsmühlenweg 9, 09599 Freiberg, Germany

11. Matthias Bauer corresponding

    Paderborn University

    Affiliation as printed

    Department of Chemistry and Center for Sustainable Systems Design (CSSD), Paderborn University, Warburger Straße 100, 33098 Paderborn, Germany