Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Article
  • Published:

Real-time impedance monitoring of oxygen reduction during surface modification of thin film cathodes

Nature Materials volume 16, pages 640–645 (2017)Cite this article

Subjects

Abstract

Improvement of solid oxide fuel cells strongly relies on the development of cathode materials with high catalytic activity for the oxygen reduction reaction. Excellent activity was found for perovskite-type oxides such as La1−xSrxCoO3−δ (LSC), but performance degradation, probably caused by surface composition changes, hinders exploitation of the full potential of LSC. This study reveals that the potentially very high activity of the LSC surface can be traced back to few very active sites. Already tiny amounts of SrO, for example, 4% of a monolayer, deposited on an LSC surface, lead to severe deactivation. Co, on the other hand, causes (re-)activation, suggesting that active sites are strongly related to Co being present at the surface. These insights could be gained by a novel method to measure changes of the electrochemical performance of thin film electrodes in situ, while modifying their surface: impedance spectroscopy measurements during deposition of well-defined fractions of monolayers of Sr-, Co- and La-oxides by single laser pulses in a pulsed laser deposition chamber.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Figure 1: Sketch of an LSC electrode with an inhomogeneously active surface for the oxygen reduction reaction (ORR).
Figure 2: The in situ impedance setup for PLD (IPLD).
Figure 3: Modification of impedance spectra by surface decoration.
Figure 4: Changes of the Rsurf exch after decorating as-deposited LSC thin films with different materials in the IPLD setup.
Figure 5: Variation of the surface exchange resistance by two decorating oxides.
Figure 6: Sketch of the model of inhomogeneously active LSC surfaces for the ORR.

Similar content being viewed by others

References

  1. Boukamp, B. A. Fuel cells: the amazing perovskite anode. Nat. Mater. 2, 294–296 (2003).

    Article  CAS  Google Scholar 

  2. Choi, S. et al. Highly efficient and robust cathode materials for low-temperature solid oxide fuel cells: PrBa0.5Sr0.5Co2−xFexO5+δ . Sci. Rep. 3, 2426 (2013).

    Article  Google Scholar 

  3. Shao, Z. & Haile, S. M. A high-performance cathode for the next generation of solid-oxide fuel cells. Nature 431, 170–173 (2004).

    Article  CAS  Google Scholar 

  4. Rupp, G. M., Schmid, A., Nenning, A. & Fleig, J. The superior properties of La0.6Ba0.4CoO3−δ thin film electrodes for oxygen exchange in comparison to La0.6Sr0.4CoO3−δ . J. Electrochem. Soc. 163, F564–F573 (2016).

    Article  CAS  Google Scholar 

  5. Baumann, F. S. et al. Quantitative comparison of mixed conducting SOFC cathode materials by means of thin film model electrodes. J. Electrochem. Soc. 154, B931–B941 (2007).

    Article  CAS  Google Scholar 

  6. Cai, Z., Kubicek, M., Fleig, J. & Yildiz, B. Chemical heterogeneities on La0.6Sr0.4CoO3−δ thin films—correlations to cathode surface activity and stability. Chem. Mater. 24, 1116–1127 (2012).

    Article  CAS  Google Scholar 

  7. De Souza, R. A. & Kilner, J. A. Oxygen transport in La1−xSrxMn1−yCoyO3+/−δ perovskites—Part I. Oxygen tracer diffusion. Solid State Ion. 106, 175–187 (1998).

    Article  CAS  Google Scholar 

  8. Van der Haar, L. M., Den Otter, M. W., Morskate, M., Bouwmeester, H. J. M. & Verweij, H. Chemical diffusion and oxygen surface transfer of La1−xSrxCoO3−δ studied with electrical conductivity relaxation. J. Electrochem. Soc. 149, J41–J46 (2002).

    Article  CAS  Google Scholar 

  9. La O, G. J. et al. Catalytic activity enhancement for oxygen reduction on epitaxial perovskite thin films for solid-oxide fuel cells. Angew. Chem. Int. Ed. 49, 5344–5347 (2010).

    Article  CAS  Google Scholar 

  10. Rupp, G. M. et al. Surface chemistry of La0.6Sr0.4CoO3−δ thin films and its impact on the oxygen surface exchange resistance. J. Mater. Chem. A 3, 22759–22769 (2015).

    Article  CAS  Google Scholar 

  11. Huber, A.-K. et al. In situ study of activation and de-activation of LSM fuel cell cathodes—electrochemistry and surface analysis of thin-film electrodes. J. Catalys. 294, 79–88 (2012).

    Article  CAS  Google Scholar 

  12. Wang, W. & Jiang, S. P. A mechanistic study on the activation process of (La, Sr)MnO3 electrodes of solid oxide fuel cells. Solid State Ion. 177, 1361–1369 (2006).

    Article  CAS  Google Scholar 

  13. Hu, B., Mahapatra, M. K. & Singh, P. Performance regeneration in lanthanum strontium manganite cathode during exposure to H2O and CO2 containing ambient air atmospheres. J. Ceram. Soc. Japan 123, 199–204 (2015).

    Article  CAS  Google Scholar 

  14. Kubicek, M., Limbeck, A., Fromling, T., Hutter, H. & Fleig, J. Relationship between cation segregation and the electrochemical oxygen reduction kinetics of La0.6Sr0.4CoO3−δ thin film electrodes. J. Electrochem. Soc. 158, B727–B734 (2011).

    Article  CAS  Google Scholar 

  15. Baumann, F. S. et al. Strong performance improvement of La0.6Sr0.4Co0.8Fe0.2O3−δ SOFC cathodes by electrochemical activation. J. Electrochem. Soc. 152, A2074–A2079 (2005).

    Article  CAS  Google Scholar 

  16. Wang, H. et al. Mechanisms of performance degradation of (La, Sr)(Co, Fe)O3−δ solid oxide fuel cell cathodes. J. Electrochem. Soc. 163, F581–F585 (2016).

    Article  CAS  Google Scholar 

  17. Oh, D., Gostovic, D. & Wachsman, E. D. Mechanism of La0.6Sr0.4Co0.2Fe0.8O3 cathode degradation. J. Mater. Res. 27, 1992–1999 (2012).

    Article  CAS  Google Scholar 

  18. Chen, Y. et al. Impact of Sr segregation on the electronic structure and oxygen reduction activity of SrTi1−xFexO3 surfaces. Energy Environ. Sci. 5, 7979–7988 (2012).

    Article  CAS  Google Scholar 

  19. Jung, W. & Tuller, H. L. Investigation of surface Sr segregation in model thin film solid oxide fuel cell perovskite electrodes. Energy Environ. Sci. 5, 5370–5378 (2012).

    Article  CAS  Google Scholar 

  20. Kim, Y.-M., Chen, X., Jiang, S. P. & Bae, J. Effect of strontium content on chromium deposition and poisoning in Ba1−xSrxCo0.8Fe0.2O3−δ (0.3 ≤ x ≥ 0.7) cathodes of solid oxide fuel cells. J. Electrochem. Soc. 159, B185–B194 (2011).

    Article  Google Scholar 

  21. Bucher, E., Gspan, C., Hofer, F. & Sitte, W. Sulphur poisoning of the SOFC cathode material La0.6Sr0.4CoO3−δ . Solid State Ion. 238, 15–23 (2013).

    Article  CAS  Google Scholar 

  22. Bucher, E., Sitte, W., Klauser, F. & Bertel, E. Impact of humid atmospheres on oxygen exchange properties, surface-near elemental composition, and surface morphology of La0.6Sr0.4CoO3−δ . Solid State Ion. 208, 43–51 (2012).

    Article  CAS  Google Scholar 

  23. Crumlin, E. J. et al. Oxygen electrocatalysis on epitaxial La0.6Sr0.4CoO3−δ Perovskite thin films for solid oxide fuel cells. J. Electrochem. Soc. 159, F219–F225 (2012).

    Article  CAS  Google Scholar 

  24. Wilson, J. R., Sase, M., Kawada, T. & Adler, S. B. Measurement of oxygen exchange kinetics on thin-film La0.6Sr0.4CoO3−δ using nonlinear electrochemical impedance spectroscopy. Electrochem. Solid-State Lett. 10, B81–B86 (2007).

    Article  CAS  Google Scholar 

  25. Baumann, F. S., Maier, J. & Fleig, J. The polarization resistance of mixed conducting SOFC cathodes: a comparative study using thin film model electrodes. Solid State Ion. 179, 1198–1204 (2008).

    Article  CAS  Google Scholar 

  26. Kawada, T. et al. Determination of oxygen vacancy concentration in a thin film of La0.6Sr0.4CoO3−δ by an electrochemical method. J. Electrochem. Soc. 149, E252–E259 (2002).

    Article  CAS  Google Scholar 

  27. Tsvetkov, N., Lu, Q., Sun, L., Crumlin, E. J. & Yildiz, B. Improved chemical and electrochemical stability of perovskite oxides with less reducible cations at the surface. Nat. Mater. 15, 1010–1016 (2016).

    Article  CAS  Google Scholar 

  28. Yu, A. S., Küngas, R., Vohs, J. M. & Gorte, R. J. Modification of SOFC cathodes by atomic layer deposition. J. Electrochem. Soc. 160, F1225–F1231 (2013).

    Article  CAS  Google Scholar 

  29. Crumlin, E. J. et al. Surface strontium enrichment on highly active perovskites for oxygen electrocatalysis in solid oxide fuel cells. Energy Environ. Sci. 5, 6081–6088 (2012).

    Article  CAS  Google Scholar 

  30. Mutoro, E., Crumlin, E. J., Biegalski, M. D., Christen, H. M. & Shao-Horn, Y. Enhanced oxygen reduction activity on surface-decorated perovskite thin films for solid oxide fuel cells. Energy Environ. Sci. 4, 3689–3696 (2011).

    Article  CAS  Google Scholar 

  31. Kuhn, M., Hashimoto, S., Sato, K., Yashiro, K. & Mizusaki, J. Oxygen nonstoichiometry and thermo-chemical stability of La0.6Sr0.4CoO3−δ . J. Solid State Chem. 197, 38–45 (2013).

    Article  CAS  Google Scholar 

  32. Kubicek, M. et al. Cation diffusion in La0.6Sr0.4CoO3−δ below 800 °C and its relevance for Sr segregation. Phys. Chem. Chem. Phys. 16, 2715–2726 (2014).

    Article  CAS  Google Scholar 

  33. Baumann, F. S., Fleig, J., Habermeier, H. & Maier, J. Impedance spectroscopic study on well-defined (La, Sr)(Co, Fe)O3−δ model electrodes. Solid State Ion. 177, 1071–1081 (2006).

    Article  CAS  Google Scholar 

  34. Hjalmarsson, P., Søgaard, M. & Mogensen, M. Electrochemical performance and degradation of (La0.6Sr0.4)0.99CoO3−δ as porous SOFC-cathode. Solid State Ion. 179, 1422–1426 (2008).

    Article  CAS  Google Scholar 

  35. Chen, Y. et al. Segregated chemistry and structure on (001) and (100) surfaces of (La1−xSrx)2CoO4 override the crystal anisotropy in oxygen exchange kinetics. Chem. Mater. 27, 5436–5450 (2015).

    Article  CAS  Google Scholar 

  36. Mogensen, M. B. et al. New hypothesis for SOFC ceramic oxygen electrode mechanisms. ECS Trans. 72, 93–103 (2016).

    Article  CAS  Google Scholar 

  37. Maier, J. in Physical Chemistry of Ionic Materials: Ions and Electrons in Solids Ch. 7.3, 433–434 (John Wiley, 2004).

    Book  Google Scholar 

  38. Pechini, M. P. Method of preparing lead and alkaline earth titanates and niobates and coating method using the same to form a capacitor. US patent 3330697 A (1967).

  39. Rupp, G. M. et al. Correlating surface cation composition and thin film microstructure with the electrochemical performance of lanthanum strontium cobaltite (LSC) electrodes. J. Mater. Chem. A 2, 7099–7108 (2014).

    Article  CAS  Google Scholar 

  40. Limbeck, A. et al. Dynamic etching of soluble surface layers with on-line inductively coupled plasma mass spectrometry detection—a novel approach for determination of complex metal oxide surface cation stoichiometry. J. Anal. Atom. Spectr. 31, 1638–1646 (2016).

    Article  CAS  Google Scholar 

  41. Kubicek, M. et al. Tensile lattice strain accelerates oxygen surface exchange and diffusion in La1−xSrxCoO3−δ thin films. ACS Nano 7, 3276–3286 (2013).

    Article  CAS  Google Scholar 

Download references

Acknowledgements

The authors gratefully acknowledge funding by Austrian Science Fund (FWF) project P4509-N16 and W1243-N16. Scanning electron microscope images were obtained using facilities at the University Service Centre for Transmission Electron Microscopy, Vienna University of Technology, Austria.

Author information

Authors and Affiliations

  1. Institute of Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9, Vienna A-1060, Austria

    Ghislain M. Rupp, Alexander K. Opitz, Andreas Nenning, Andreas Limbeck & Jürgen Fleig

Authors
  1. Ghislain M. Rupp
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Alexander K. Opitz
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Andreas Nenning
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Andreas Limbeck
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Jürgen Fleig
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

G.M.R. prepared the samples, developed the IPLD setup, performed and analysed impedance, X-ray diffraction and ICP measurements and wrote the manuscript. A.K.O. had the initial idea for the IPLD setup, supported the development and was involved at all stages of the study from planning to data analysis and discussion. A.N. performed XPS measurements and analysis. A.L. supervised the ICP measurements and was involved in the interpretation of the data. J.F. supervised all impedance spectroscopy measurements and was involved in the interpretation of the results as well as the preparation of the manuscript.

Corresponding author

Correspondence to Ghislain M. Rupp.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Information (PDF 1615 kb)

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Rupp, G., Opitz, A., Nenning, A. et al. Real-time impedance monitoring of oxygen reduction during surface modification of thin film cathodes. Nature Mater 16, 640–645 (2017). https://doi.org/10.1038/nmat4879

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nmat4879

This article is cited by

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing