Electrochemical properties of Metal Oxide Epitaxial Catalysts

• Applicant: Professor Dr. Olaf Magnussen
• Subject Area: Physical Chemistry of Solids and Surfaces, Material Characterisation ; Experimental Condensed Matter Physics
• Term: from 2015 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 284207613

• Final Report Year: 2020

Final Report Abstract

In this project, we performed studies aiming at a better microscopic understanding of iron-group oxide electrocatalysts for oxygen evolution, focusing on Co and Fe oxides. We developed experimental approaches for the preparation of model oxide catalysts with well-defined surface structure, specifically Co3O4(111), CoOOH(001), Fe3O4(111) and (FexCo1-x)3O4(111) thin film electrodes and Fe3O4(100) single crystals. As new experimental tools, new instrumentation and methods for in situ and operando studies were developed that enabled obtaining structural data under conditions resembling those in technological processes. In combination with in situ X-ray absorbtion spectroscopy, microscopic methods and electrochemical measurements, these revealed complex potentialdependent structural changes of the model oxide catalysts that were affected by pH as well as sample history and morphology. In particularly, our studies revealed the formation of ultrathin skin layers with altered structure and higher oxidation state, which seem to play a significant role in the electrocatalytic reactivity of these materials. In summary, these studies provided significant advances towards an improved fundamental understanding of these electrode materials, both from a methodolocical point of view and in terms of the obtained microscopic insights.

Publications

• Transmission surface diffraction for in operando studies of heterogeneous interfaces, J. Phys. Chem. Lett., 8, 1067-1071 (2017)
  F. Reikowski, T. Wiegmann, J. Stettner, J. Drnec, V. Honkimäki, F. Maroun, P. Allongue, O.M. Magnussen
  (See online at https://doi.org/10.1021/acs.jpclett.7b00332)
• Potential dependence of the structure and magnetism of electrodeposited Pd/Co/Au(111) layers, J. Electroanal. Chem., 819, 322-330 (2018)
  F. Maroun, F. Reikowski, T. Wiegmann, N. Di, J. Stettner, O.M. Magnussen, P. Allongue, J.
  (See online at https://doi.org/10.1016/j.jelechem.2017.11.002)
• Operando Surface X-ray Diffraction Studies of Structurally-defined Co3O4 and CoOOH Thin Films during Oxygen Evolution, ACS Catalysis, 9, 3811-3821 (2019)
  F. Reikowski, F. Maroun, I. Pacheco, T. Wiegmann, P. Allongue, J. Stettner, O.M. Magnussen
  (See online at https://doi.org/10.1021/acscatal.8b04823)
• Electrochemical stability of the reconstructed Fe3O4(001) surface, Angew. Chem. Int. Ed. (2020)
  D. Grumelli, T. Wiegmann, S. Barja, F. Reikowski, F. Maroun, P. Allongue, J. Balajka, G.S. Parkinson, U. Diebold, K. Kern, O.M. Magnussen
  (See online at https://doi.org/10.1002/anie.202008785)
• In situ transmission X-ray micro-diffraction from thin metal films electrodeposited in microfluidic channels, J. Electrochem. Soc., 167, 112505 1-8 (2020)
  T. Wiegmann, J. Drnec, F. Reikowski, J. Stettner, F. Maroun, O. M. Magnussen
  (See online at https://doi.org/10.1149/1945-7111/aba077)