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Unravelling the complex causality behind Fe–N–C degradation in fuel cells

Nature Catalysis volume 6, pages 1140–1150 (2023)Cite this article

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Abstract

Beyond great advances in initial activity, Fe–N–C catalysts face the next challenge of stability issue in acidic medium that must be overcome to replace Pt in fuel cell cathode. However, the complex phenomena in fuel cells and consequential difficulty in understanding deactivation mechanisms of Fe–N–C cathodes impede solutions for prolonged stability. Here we show time-resolved changes in active site density and turnover frequency of Fe–N–C along with concurrent decrease in oxygen reduction reaction current in a temperature/gas controllable gas-diffusion electrode flow cell. Operando diagnosis of Fe leaching identifies a strong dependence of site density changes on operating parameters and draws a lifetime-dependent stability diagram that reveals a shift in the prime degradation mechanism during operation. A proof-of-concept strategy with site-isolated Pt ions as a non-catalytic stabilizer, supported by theoretical calculations, demonstrates enhanced fuel cell stability with reduced Fe dissolution, offering design principles for durable Fe–N–C catalysts.

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Fig. 1: Effects of temperature on Fe dissolution of Fe0.5NC.
Fig. 2: Effects of Ar and O2 gases on Fe dissolution of Fe0.5NC.
Fig. 3: Physical and electrochemical characterizations of Fe0.5NC–Pt.
Fig. 4: Proof-of-concept strategy with isolated Pt ion as a stabilizer of Fe–N4 sites.

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Data availability

The data generated in this study have been deposited in the Zenodo repository database without accession code (https://doi.org/10.5281/zenodo.8287921)52. The DFT data generated in this study have been deposited in the Zenodo repository database without accession code (https://doi.org/10.5281/zenodo.8287952)53. Additional data supporting the findings of this study are available from the corresponding author upon reasonable request.

References

  1. Yoshida, T. & Kojima, K. Toyota MIRAI fuel cell vehicle and progress toward a future hydrogen society. Electrochem. Soc. Interface 24, 45–49 (2015).

    CAS  Google Scholar 

  2. Thompson, S. T. & Papageorgopoulos, D. Platinum group metal-free catalysts boost cost competitiveness of fuel cell vehicles. Nat. Catal. 2, 558–561 (2019).

    CAS  Google Scholar 

  3. Proietti, E. et al. Iron-based cathode catalyst with enhanced power density in polymer electrolyte membrane fuel cells. Nat. Commun. 2, 416 (2011).

    PubMed  Google Scholar 

  4. Chung, H. T. et al. Direct atomic-level insight into the active sites of a high-performance PGM-free ORR catalyst. Science 357, 479–484 (2017).

    CAS  PubMed  Google Scholar 

  5. Lefèvre, M., Proietti, E., Jaouen, F. & Dodelet, J.-P. Iron-based catalysts with improved oxygen reduction activity in polymer electrolyte fuel cells. Science 324, 71–74 (2009).

    PubMed  Google Scholar 

  6. Yin, X. & Zelenay, P. (Invited) Kinetic models for the degradation mechanisms of PGM-free ORR catalysts. ECS Trans. 85, 1239–1250 (2018).

    CAS  Google Scholar 

  7. Chenitz, R. et al. A specific demetalation of Fe–N4 catalytic sites in the micropores of NC_Ar + NH3 is at the origin of the initial activity loss of the highly active Fe/N/C catalyst used for the reduction of oxygen in PEM fuel cells. Energy Environ. Sci. 11, 365–382 (2018).

    CAS  Google Scholar 

  8. Zhang, G. et al. Non-PGM electrocatalysts for PEM fuel cells: effect of fluorination on the activity and stability of a highly active NC_Ar + NH3 catalyst. Energy Environ. Sci. 12, 3015–3037 (2019).

    CAS  Google Scholar 

  9. Choi, C. H. et al. Stability of Fe–N–C catalysts in acidic medium studied by operando spectroscopy. Angew. Chem. Int. Ed. 54, 12753–12757 (2015).

    CAS  Google Scholar 

  10. Choi, C. H. et al. Minimizing operando demetallation of Fe–N–C electrocatalysts in acidic medium. ACS Catal. 6, 3136–3146 (2016).

    CAS  Google Scholar 

  11. Kumar, K. et al. Fe–N–C electrocatalysts’ durability: effects of single atoms’ mobility and clustering. ACS Catal. 11, 484–494 (2021).

    CAS  Google Scholar 

  12. Kumar, K. et al. On the influence of oxygen on the degradation of Fe–N–C catalysts. Angew. Chem. Int. Ed. 59, 3235–3243 (2020).

    CAS  Google Scholar 

  13. Herranz, J. et al. Unveiling N-protonation and anion-binding effects on Fe/N/C catalysts for O2 reduction in proton-exchange-membrane fuel cells. J. Phys. Chem. C 115, 16087–16097 (2011).

    CAS  Google Scholar 

  14. Choi, C. H. et al. The Achilles’ heel of iron-based catalysts during oxygen reduction in an acidic medium. Energy Environ. Sci. 11, 3176–3182 (2018).

    CAS  Google Scholar 

  15. Ehelebe, K., Escalera-López, D. & Cherevko, S. Limitations of aqueous model systems in the stability assessment of electrocatalysts for oxygen reactions in fuel cell and electrolyzers. Curr. Opin. Electrochem. 29, 100832 (2021).

    CAS  Google Scholar 

  16. Li, J. et al. Identification of durable and non-durable FeNx sites in Fe–N–C materials for proton exchange membrane fuel cells. Nat. Catal. 4, 10–19 (2021).

    Google Scholar 

  17. Snitkoff-Sol, R. Z. et al. Quantifying the electrochemical active site density of precious metal-free catalysts in situ in fuel cells. Nat. Catal. 5, 163–170 (2022).

    CAS  Google Scholar 

  18. Xie, H. et al. Ta–TiOx nanoparticles as radical scavengers to improve the durability of Fe–N–C oxygen reduction catalysts. Nat. Energy 7, 281–289 (2022).

    CAS  Google Scholar 

  19. Liu, S. et al. Atomically dispersed iron sites with a nitrogen–carbon coating as highly active and durable oxygen reduction catalysts for fuel cells. Nat. Energy 7, 652–663 (2022).

    CAS  Google Scholar 

  20. Zitolo, A. et al. Identification of catalytic sites for oxygen reduction in iron- and nitrogen-doped graphene materials. Nat. Mater. 14, 937–942 (2015).

    CAS  PubMed  Google Scholar 

  21. Kim, D. H. et al. Selective electrochemical reduction of nitric oxide to hydroxylamine by atomically dispersed iron catalyst. Nat. Commun. 12, 1856 (2021).

    CAS  PubMed  PubMed Central  Google Scholar 

  22. Goellner, V. et al. Degradation of Fe/N/C catalysts upon high polarization in acid medium. Phys. Chem. Chem. Phys. 16, 18454–18462 (2014).

    CAS  PubMed  Google Scholar 

  23. Chen, Z. et al. Operando characterization of iron phthalocyanine deactivation during oxygen reduction reaction using electrochemical tip-enhanced Raman spectroscopy. J. Am. Chem. Soc. 141, 15684–15692 (2019).

    CAS  PubMed  Google Scholar 

  24. Holby, E. F., Wang, G. & Zelenay, P. Acid stability and demetalation of PGM-free ORR electrocatalyst structures from density functional theory: a model for ‘single-atom catalyst’ dissolution. ACS Catal. 10, 14527–14539 (2020).

    CAS  Google Scholar 

  25. Jia, Q. et al. Spectroscopic insights into the nature of active sites in iron–nitrogen–carbon electrocatalysts for oxygen reduction in acid. Nano Energy 29, 65–82 (2016).

    CAS  Google Scholar 

  26. Beverskog, B. & Puigdomenech, I. Revised pourbaix diagrams for iron at 25–300 °C. Corros. Sci. 38, 2121–2135 (1996).

    CAS  Google Scholar 

  27. Parida, K. M. & Das, N. N. Reductive dissolution of hematite in hydrochloric acid medium by some inorganic and organic reductants: a comparative study. Indian J. Eng. Mater. Sci. 3, 243 (1996).

    CAS  Google Scholar 

  28. Bae, G. et al. Quantification of active site density and turnover frequency: from single-atom metal to nanoparticle electrocatalysts. JACS Au 1, 586–597 (2021).

    CAS  PubMed  PubMed Central  Google Scholar 

  29. Malko, D., Kucernak, A. & Lopes, T. In situ electrochemical quantification of active sites in Fe–N/C non-precious metal catalysts. Nat. Commun. 7, 13285 (2016).

    CAS  PubMed  PubMed Central  Google Scholar 

  30. Lei, M. et al. CeO2 nanocubes-graphene oxide as durable and highly active catalyst support for proton exchange membrane fuel cell. Sci. Rep. 4, 7415 (2014).

    CAS  PubMed  PubMed Central  Google Scholar 

  31. Wang, L., Advani, S. G. & Prasad, A. K. Degradation reduction of polymer electrolyte membranes using CeO2 as a free-radical scavenger in catalyst layer. Electrochim. Acta 109, 775–780 (2013).

    CAS  Google Scholar 

  32. Bae, G., Chung, M. W., Ji, S. G., Jaouen, F. & Choi, C. H. pH effect on the H2O2-induced deactivation of Fe–N–C catalysts. ACS Catal. 10, 8485–8495 (2020).

    CAS  Google Scholar 

  33. Mechler, A. K. et al. Stabilization of iron-based fuel cell catalysts by non-catalytic platinum. J. Electrochem. Soc. 165, F1084–F1091 (2018).

    CAS  Google Scholar 

  34. Xiao, F. et al. Atomically dispersed Pt and Fe sites and Pt–Fe nanoparticles for durable proton exchange membrane fuel cells. Nat. Catal. 5, 503–512 (2022).

    CAS  Google Scholar 

  35. Choi, C. H. et al. Hydrogen peroxide synthesis via enhanced two-electron oxygen reduction pathway on carbon-coated Pt surface. J. Phys. Chem. C 118, 30063–30070 (2014).

    CAS  Google Scholar 

  36. Ferre-Vilaplana, A., Perales-Rondón, J. V., Buso-Rogero, C., Feliu, J. M. & Herrero, E. Formic acid oxidation on platinum electrodes: a detailed mechanism supported by experiments and calculations on well-defined surfaces. J. Mater. Chem. A 5, 21773–21784 (2017).

    CAS  Google Scholar 

  37. Chung, D. Y., Lee, K.-J. & Sung, Y.-E. Methanol electro-oxidation on the Pt surface: revisiting the cyclic voltammetry interpretation. J. Phys. Chem. C 120, 9028–9035 (2016).

    CAS  Google Scholar 

  38. Neyerlin, K. C. et al. A. Study of the exchange current density for the hydrogen oxidation and evolution reactions. J. Electrochem. Soc. 154, B631–B635 (2007).

    CAS  Google Scholar 

  39. Zhang, G. et al. Is iron involved in the lack of stability of Fe/N/C electrocatalysts used to reduce oxygen at the cathode of PEM fuel cells? Nano Energy 29, 111–125 (2016).

  40. Kida, K., Okita, M., Fujita, K., Tanaka, S. & Miyake, Y. Formation of high crystalline ZIF-8 in an aqueous solution. Cryst. Eng. Comm. 15, 1794–1801 (2013).

    CAS  Google Scholar 

  41. Sa, Y. J. et al. A general approach to preferential formation of active Fe–Nx sites in Fe–N/C electrocatalysts for efficient oxygen reduction reaction. J. Am. Chem. Soc. 138, 15046–15056 (2016).

    CAS  PubMed  Google Scholar 

  42. Badam, R. et al. Sacrificial reducing agent free photo-generation of platinum nano particle over carbon/TiO2 for highly efficient oxygen reduction reaction. Sci. Rep. 6, 37006 (2016).

  43. Kresse, G. & Furthmüller, J. Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set. Comput. Mater. Sci. 6, 15–50 (1996).

    CAS  Google Scholar 

  44. Kresse, G. & Furthmüller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B 54, 11169 (1996).

    CAS  Google Scholar 

  45. Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77, 3865 (1996).

  46. Methfessel, M. & Paxton, A. T. High-precision sampling for Brillouin-zone integration in metals. Phys. Rev. B 40, 3616 (1989).

  47. Henkelman, G., Arnaldsson, A. & Jónsson, H. A fast and robust algorithm for Bader decomposition of charge density. Comput. Mater. Sci. 36, 354–360 (2006).

    Google Scholar 

  48. Becke, A. D. Density‐functional thermochemistry. III. The role of exact exchange. J. Chem. Phys. 98, 5648–5652 (1993).

    CAS  Google Scholar 

  49. Hay, P. J. & Wadt, W. R. Ab initio effective core potentials for molecular calculations. Potentials for the transition metal atoms Sc to Hg. J. Chem. Phys. 82, 270–283 (1985).

    CAS  Google Scholar 

  50. Bochevarov, A. D. et al. Jaguar: A high-performance quantum chemistry software program with strengths in life and materials sciences. Int. J. Quantum Chem. 113, 2110–2142 (2013).

    CAS  Google Scholar 

  51. Friedrichs, M., Zhou, R., Edinger, S. R. & Friesner, R. A. Poisson–Boltzmann analytical gradients for molecular modeling calculations. J. Phys. Chem. B 103, 3057–3061 (1999).

    CAS  Google Scholar 

  52. Bae, G. et al. Unraveling the complex causality behind Fe–N–C degradation in fuel cells. Zenodo https://doi.org/10.5281/zenodo.8287921 (2023).

  53. Bae, G. et al. Unraveling the complex causality behind Fe–N–C degradation in fuel cells. Zenodo https://doi.org/10.5281/zenodo.8287952 (2023).

    Article  Google Scholar 

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Acknowledgements

This research was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (nos. 2019M3D1A1079309, 2021R1A5A1030054 and 2023R1A2C2005278 to C.H.C.) and by the KIST Institutional Program. We acknowledge the Pohang Accelerator Laboratory (PAL) for beamline use (8C, PLS-II). We are grateful to M. H. Seo and S. Jin for helpful discussions on this paper.

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Author notes

  1. These authors contributed equally: Geunsu Bae, Minho M. Kim, Man Ho Han.

Authors and Affiliations

  1. Department of Chemistry, Pohang University of Science and Technology, Pohang, Republic of Korea

    Geunsu Bae, Junsic Cho, Dong Hyun Kim & Chang Hyuck Choi

  2. Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea

    Minho M. Kim & Hyungjun Kim

  3. Clean Energy Research Center, Korea Institute of Science and Technology, Seoul, Republic of Korea

    Man Ho Han & Hyung-Suk Oh

  4. ICGM, University of Montpellier, CNRS, ENSCM, Montpellier, France

    Moulay-Tahar Sougrati & Frédéric Jaouen

  5. Department of Chemistry, Seoul National University, Seoul, Republic of Korea

    Jinjong Kim & Sang Hoon Joo

  6. Beamline Department, Pohang Accelerator Laboratory, Pohang University of Science and Technology, Pohang, Republic of Korea

    Kug-Seung Lee

  7. Materials and Process Simulation Center, California Institute of Technology, Pasadena, CA, USA

    William A. Goddard III

  8. KIST-SKKU Carbon-Neutral Research Center, Sungkyunkwan University, Suwon, Republic of Korea

    Hyung-Suk Oh

  9. Institute for Convergence Research and Education in Advanced Technology (I–CREATE), Yonsei University, Seoul, Republic of Korea

    Chang Hyuck Choi

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  1. Geunsu Bae
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Contributions

C.H.C., F.J., H.K. and H.-S.O. conceived and supervised the project. G.B. conducted most of the experimental analyses. M.M.K. conducted DFT calculations. M.H.H. conducted fuel cell experiment. J.C. and D.H.K. contributed to the part of electrochemical analyses. M.-T.S. contributed to 57Fe Mössbauer spectroscopy measurement. K.-S.L contributed to XAS measurement. J.K. and S.H.J. contributed to part of the catalyst synthesis. W.A.G. contributed to DFT calculations. The paper was written through the contributions of all authors.

Corresponding authors

Correspondence to Hyung-Suk Oh, Hyungjun Kim, Frédéric Jaouen or Chang Hyuck Choi.

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Nature Catalysis thanks Lior Elbaz, Michael Bron and Zheng Wang for their contribution to the peer review of this work.

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Supplementary Notes 1–8, Figs. 1–47, Tables 1–4 and references.

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Bae, G., Kim, M.M., Han, M.H. et al. Unravelling the complex causality behind Fe–N–C degradation in fuel cells. Nat Catal 6, 1140–1150 (2023). https://doi.org/10.1038/s41929-023-01039-7

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