Atomic-scale studies of catalysis
by spinel oxides

Subproject P04

The spinel class of metal oxides hosts diverse materials, some of which make excellent catalysts. Fe3O4 is already the industrial catalyst for the high-temperature water-gas shift reaction (CO+H2O -> H2+CO2), but research is needed to identify the optimal replacement for the toxic Cr promoter/stabilizer. Ternary MeFe2O4 compounds (Me=Fe, Ni, Co, Mn) are active and stable for the electrochemical oxygen evolution reaction (OER). However, the structure of the active catalyst and the reaction mechanisms are unknown. While these reactions appear different, both clearly benefit from a combination of multivalent cations in the surface layers.

In this project, we will seek to learn why, using a combination of atomic-scale imaging, a host of spectroscopies, and theory. We will dope the Fe3O4(001) surface with 3d transition metals and investigate how the adsorption energies, XPS binding energies, and IRAS frequencies of H2O, CO, CO2, O2, and H2 change with sample composition all the way from isolated dopants to ternary thin films. We will use the data obtained in tightly-controlled UHV experiments to:

i) Interpret the reactivity of our model catalysts under realistic HTWGS and OER conditions.

ii) Provide the benchmark data for experiments on nominally similar powder catalysts (P10 Föttinger).

iii) Support the development of theoretical modeling (P07 Franchini).

A joint postdoc (P04-P11) will facilitate the new collaboration with P11 Backus.

Gareth S. Parkinson
PI

Expertise

The group focuses on understanding mechanisms of catalytic reactions using a combination of experimental surface science and theoretical calculations. We have access to a total of seven ultrahigh-vacuum (UHV) chambers, which allows us to conduct the following experiments:
  • Scanning Tunneling Microscopy (STM) (in UHV 4K – 300 K, electrochemical STM)
  • Atomic Force Microscopy (AFM): UHV-based (q+ sensor) and in the ambient (cantilever-based)
  • Low-Energy Electron Diffraction (LEED)
  • Reflection High Energy Diffraction (RHEED)
  • X-ray Photoelectron Spectroscopy (XPS)
  • Ultraviolet Photoelectron Spectroscopy (UPS)
  • Auger Electron Spectroscopy (AES)
  • Low-energy He+ ion scattering (LEIS)
  • Thermal Programmed Desorption Spectroscopy (TPD)
Of particular use for TACO is our surface reactivity chamber, which is specifically designed to study single-crystal metal-oxide samples. Reactants are delivered to the sample by molecular beams, and products detected by a mass spectrometer. In addition to TPD, XPS, UPS, and LEIS, we will soon be able to perform infrared absorption spectroscopy (IRAS) experiments on these samples using an optimized beam geometry.

Team

Gareth S. Parkinson
PI

Publications

2021

Ni-modified Fe3O4(001) surface as a simple model system for understanding the oxygen evolution reaction

Mirabella, Francesca; Müllner, Matthias; Touzalin, Thomas; Riva, Michele; Jakub, Zdenek; Kraushofer, Florian; Schmid, Michael; Koper, Marc T M; Parkinson, Gareth S; Diebold, Ulrike

Ni-modified Fe3O4(001) surface as a simple model system for understanding the oxygen evolution reaction Journal Article

In: Electrochimica Acta, 389 , pp. 138638, 2021.

Abstract | Links | BibTeX | Tags: P02, P04, pre-TACO

Unraveling CO adsorption on model single-atom catalysts

Hulva, Jan; Meier, Matthias; Bliem, Roland; Jakub, Zdenek; Kraushofer, Florian; Schmid, Michael; Diebold, Ulrike; Franchini, Cesare; Parkinson, Gareth S

Unraveling CO adsorption on model single-atom catalysts Journal Article

In: Science, 371 (6527), pp. 375–379, 2021.

Abstract | Links | BibTeX | Tags: P02, P04, P07, pre-TACO

2020

IrO2 Surface Complexions Identified through Machine Learning and Surface Investigations

Timmermann, Jakob; Kraushofer, Florian; Resch, Nikolaus; Li, Peigang; Wang, Yu; Mao, Zhiqiang; Riva, Michele; Lee, Yonghyuk; Staacke, Carsten; Schmid, Michael; Scheurer, Christoph; Parkinson, Gareth S; Diebold, Ulrike; Reuter, Karsten

IrO2 Surface Complexions Identified through Machine Learning and Surface Investigations Journal Article

In: Physical Review Letters, 125 (20), pp. 206101, 2020.

Abstract | Links | BibTeX | Tags: P02, P04, pre-TACO

Electrochemical Stability of the Reconstructed Fe3O4(001) Surface

Grumelli, Doris; Wiegmann, Tim; Barja, Sara; Reikowski, Finn; Maroun, Fouad; Allongue, Philippe; Balajka, Jan; Parkinson, Gareth S; Diebold, Ulrike; Kern, Klaus; Magnussen, Olaf M

Electrochemical Stability of the Reconstructed Fe3O4(001) Surface Journal Article

In: Angewandte Chemie - International Edition, 59 (49), pp. 21904–21908, 2020.

Abstract | Links | BibTeX | Tags: P02, P04, pre-TACO

2019

Local Structure and Coordination Define Adsorption in a Model Ir1/Fe3O4 Single-Atom Catalyst

Jakub, Zdenek; Hulva, Jan; Meier, Matthias; Bliem, Roland; Kraushofer, Florian; Setvin, Martin; Schmid, Michael; Diebold, Ulrike; Franchini, Cesare; Parkinson, Gareth S

Local Structure and Coordination Define Adsorption in a Model Ir1/Fe3O4 Single-Atom Catalyst Journal Article

In: Angewandte Chemie - International Edition, 58 (39), pp. 13961–13968, 2019.

Abstract | Links | BibTeX | Tags: P02, P04, P07, pre-TACO