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Tuning the thermal activation atmosphere breaks the activity–stability trade-off of Fe–N–C oxygen reduction fuel cell catalysts

Nature Catalysis volume 6, pages 1215–1227 (2023)Cite this article

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Abstract

Fe–N–C catalysts are the most promising platinum group metal-free oxygen-reduction catalysts, but they suffer from a low density of active metal sites and the so-called activity–stability trade-off. Here we report an Fe–N–C catalyst prepared by adding an optimal amount of H2 to the traditional inert atmosphere during the thermal activation. The presence of H2 significantly increases the total density of FeN4 sites, suppressing the unstable pyrrolic-N-coordinated S1 sites and favouring the stable pyridinic-N-coordinated S2 sites with shortened Fe–N bond lengths. We propose that the intrinsically stable S2 sites are probably arranged in well-graphitized carbon layers, and the S1 sites exist in less-graphitized carbon. H2 could remove unstable S1 sites and retain stable S2 sites during the pyrolysis to break the challenging activity–stability trade-off. The Fe–N–C catalyst in membrane electrode assemblies maintains a current density of 67 mA cm−2 at 0.8 V (H2–air) after 30,000 voltage cycles (0.60 to 0.95 V under H2–air), achieving encouraging durability and performance simultaneously.

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Fig. 1: Synthesis principles and catalytic properties.
Fig. 2: MEA performance of the Fe–N–C catalysts.
Fig. 3: Analysis of Fe coordination environments induced from a pyrolysis atmosphere.
Fig. 4: Morphologies of the Fe–N–C catalysts.
Fig. 5: Structural analysis of the Fe–N–C catalysts.
Fig. 6: DFT calculations to elucidate activity and stability improvement.

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All data supporting the findings of this study are available within the paper and Supplementary Information, or from the authors upon request. Source data are provided with this paper.

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Acknowledgements

We acknowledge support from the US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office. Scanning transmission electron microscopy research was supported by the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory. This work was in part authored by Argonne National Laboratory, which is operated for the US DOE by the University of Chicago Argonne LLC under contract no. DE-AC02-06CH11357. G. Wu also thanks the New York State’s Center of Excellence in Materials Informatics (CMI) at the University at Buffalo, as well as the National Science Foundation (CBET-1604392, 1804326 and 2223467), for partial support.

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Author notes

  1. These authors contributed equally: Yachao Zeng, Chenzhao Li, Boyang Li, Jiashun Liang.

Authors and Affiliations

  1. Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York, Buffalo, NY, USA

    Yachao Zeng, Jiashun Liang, Bingzhang Zhang & Gang Wu

  2. Department of Mechanical and Energy Engineering, Purdue School of Engineering and Technology, Indiana University-Purdue University, Indianapolis, IN, USA

    Chenzhao Li & Jian Xie

  3. School of Mechanical Engineering, Purdue University, West Lafayette, IN, USA

    Chenzhao Li

  4. Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA, USA

    Boyang Li & Guofeng Wang

  5. Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, USA

    Michael J. Zachman & David A. Cullen

  6. Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA

    Raphael P. Hermann

  7. Advanced Photon Source, Argonne National Laboratory, Lemont, IL, USA

    E. Ercan Alp & Barbara Lavina

  8. Center for Advanced Radiation Sources, The University of Chicago, Chicago, IL, USA

    Barbara Lavina

  9. Department of Chemical Engineering, University of South Carolina, Columbia, SC, USA

    Stavros Karakalos

  10. School of Chemical, Biological, and Environmental Engineering, Oregon State University, Corvallis, OR, USA

    Marcos Lucero, Maoyu Wang & Zhenxing Feng

  11. Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, IL, USA

    Deborah J. Myers

  12. INRS-Énergie, Matériaux et Télécommunications, Varennes, Québec, Canada

    Jean-Pol Dodelet

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  1. Yachao Zeng
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Contributions

G. Wu, J.-P.D. and Y.Z. were the primary writers of the paper. Y.Z., J.L., B.Z., S.K. and G. Wu designed the catalyst synthesis and performed the electrochemical experiments, characterized the catalyst and analysed the data. C.L. and J.X. carried out fuel cell tests and data analysis. D.A.C. and M.J.Z. together performed the electron microscopy imaging and further characterizations. B. Li and G. Wang designed and performed DFT calculations. M.L., M.W. and Z.F. designed and performed X-ray absorption spectroscopy and data analysis. R.P.H., E.E.A., B. Lavina and D.J.M. designed and performed Mössbauer spectroscopy experiments and data analysis. G. Wu supervised the execution of the overall project.

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Correspondence to Guofeng Wang, Jian Xie, Deborah J. Myers or Gang Wu.

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Zeng, Y., Li, C., Li, B. et al. Tuning the thermal activation atmosphere breaks the activity–stability trade-off of Fe–N–C oxygen reduction fuel cell catalysts. Nat Catal 6, 1215–1227 (2023). https://doi.org/10.1038/s41929-023-01062-8

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