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Performance enhancement and degradation mechanism identification of a single-atom Co–N–C catalyst for proton exchange membrane fuel cells


The development of catalysts free of platinum-group metals and with both a high activity and durability for the oxygen reduction reaction in proton exchange membrane fuel cells is a grand challenge. Here we report an atomically dispersed Co and N co-doped carbon (Co–N–C) catalyst with a high catalytic oxygen reduction reaction activity comparable to that of a similarly synthesized Fe–N–C catalyst but with a four-time enhanced durability. The Co–N–C catalyst achieved a current density of 0.022 A cm−2 at 0.9 ViR-free (internal resistance-compensated voltage) and peak power density of 0.64 W cm−2 in 1.0 bar H2/O2 fuel cells, higher than that of non-iron platinum-group-metal-free catalysts reported in the literature. Importantly, we identified two main degradation mechanisms for metal (M)–N–C catalysts: catalyst oxidation by radicals and active-site demetallation. The enhanced durability of Co–N–C relative to Fe–N–C is attributed to the lower activity of Co ions for Fenton reactions that produce radicals from the main oxygen reduction reaction by-product, H2O2, and the significantly enhanced resistance to demetallation of Co–N–C.

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Fig. 1: Synthesis and characterization of the atomically dispersed Co–N–C catalyst.
Fig. 2: Structural characterization of the Co–N–C catalysts.
Fig. 3: RRDE and PEM fuel cell performance measurements.
Fig. 4: Catalysts durability studied on RRDE and MEA.
Fig. 5: Fundamental understanding of degradation mechanisms.

Data availability

The data that support the findings of this study are available within the paper and its Supplementary Information or from the corresponding author upon reasonable request.


  1. 1.

    Debe, M. K. Electrocatalyst approaches and challenges for automotive fuel cells. Nature 486, 43–51 (2012).

    CAS  PubMed  Google Scholar 

  2. 2.

    Wang, X. X., Swihart, M. T. & Wu, G. Achievements, challenges and perspectives on cathode catalysts in proton exchange membrane fuel cells for transportation. Nat. Catal. 2, 578–589 (2019).

    CAS  Google Scholar 

  3. 3.

    Kongkanand, A. & Mathias, M. F. The priority and challenge of high-power performance of low-platinum proton-exchange membrane fuel cells. J. Phys. Chem. Lett. 7, 1127–1137 (2016).

    CAS  PubMed  Google Scholar 

  4. 4.

    Stephens, I. E. L., Rossmeisl, J. & Chorkendorff, I. Toward sustainable fuel cells. Science 354, 1378–1379 (2016).

    CAS  PubMed  Google Scholar 

  5. 5.

    Ott, S. et al. Ionomer distribution control in porous carbon-supported catalyst layers for high-power and low Pt-loaded proton exchange membrane fuel cells. Nat. Mater. 19, 77–85 (2020).

    CAS  PubMed  Google Scholar 

  6. 6.

    Thompson, S. T. et al. Direct hydrogen fuel cell electric vehicle cost analysis: system and high-volume manufacturing description, validation, and outlook. J. Power Sources 399, 304–313 (2018).

    CAS  Google Scholar 

  7. 7.

    He, Y. H., Liu, S. W., Priest, C., Shi, Q. R. & Wu, G. Atomically dispersed metal–nitrogen–carbon catalysts for fuel cells: advances in catalyst design, electrode performance, and durability improvement. Chem. Soc. Rev. 49, 3484–3524 (2020).

    CAS  PubMed  Google Scholar 

  8. 8.

    Luo, F. et al. P-block single-metal-site tin/nitrogen-doped carbon fuel cell cathode catalyst for oxygen reduction reaction. Nat. Mater. 19, 1215–1223 (2020).

    CAS  PubMed  Google Scholar 

  9. 9.

    Shao, Y. Y., Dodelet, J. P., Wu, G. & Zelenay, P. PGM-free cathode catalysts for PEM fuel cells: a mini-review on stability challenges. Adv. Mater. 31, e1807615 (2019).

    PubMed  Google Scholar 

  10. 10.

    Barkholtz, H. M. & Liu, D. J. Advancements in rationally designed PGM-free fuel cell catalysts derived from metal–organic frameworks. Mater. Horiz. 4, 20–37 (2017).

    CAS  Google Scholar 

  11. 11.

    Gupta, S. et al. Engineering favorable morphology and structure of Fe–N–C oxygen-reduction catalysts through tuning of nitrogen/carbon precursors. Chemsuschem 10, 774–785 (2017).

    CAS  PubMed  Google Scholar 

  12. 12.

    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 

  13. 13.

    Chung, H. T. et al. Direct atomic-level insight into the active sites of a high-performance PGM-free ORR catalyst. Science 357, 479–483 (2017).

    CAS  PubMed  Google Scholar 

  14. 14.

    Chen, M. J., He, Y. H., Spendelow, J. S. & Wu, G. Atomically dispersed metal catalysts for oxygen reduction. ACS Energy Lett. 4, 1619–1633 (2019).

    CAS  Google Scholar 

  15. 15.

    Chen, Y. J. et al. Single-atom catalysts: synthetic strategies and electrochemical applications. Joule 2, 1242–1264 (2018).

    CAS  Google Scholar 

  16. 16.

    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 

  17. 17.

    Wan, X. et al. Fe–N–C electrocatalyst with dense active sites and efficient mass transport for high-performance proton exchange membrane fuel cells. Nat. Catal. 2, 259–268 (2019).

    CAS  Google Scholar 

  18. 18.

    Zhang, H. G. et al. Single atomic iron catalysts for oxygen reduction in acidic media: particle size control and thermal activation. J. Am. Chem. Soc. 139, 14143–14149 (2017).

    CAS  PubMed  Google Scholar 

  19. 19.

    Osmieri, L., Cullen, D. A., Chung, H. T., Ahluwalia, R. K. & Neyerlin, K. C. Durability evaluation of a Fe–N–C catalyst in polymer electrolyte fuel cell environment via accelerated stress tests. Nano Energy 78, 105209 (2020).

    CAS  Google Scholar 

  20. 20.

    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 

  21. 21.

    Lefevre, M. & Dodelet, J. P. Fe-based catalysts for the reduction of oxygen in polymer electrolyte membrane fuel cell conditions: determination of the amount of peroxide released during electroreduction and its influence on the stability of the catalysts. Electrochim. Acta 48, 2749–2760 (2003).

    CAS  Google Scholar 

  22. 22.

    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 

  23. 23.

    Santori, P. G. et al. Effect of pyrolysis atmosphere and electrolyte pH on the oxygen reduction activity, stability and spectroscopic signature of FeNx moieties in Fe–N–C catalysts. J. Electrochem. Soc 166, F3311 (2019).

    CAS  Google Scholar 

  24. 24.

    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 

  25. 25.

    Ramaswamy, N., Hakim, N. & Mukerjee, S. Degradation mechanism study of perfluorinated proton exchange membrane under fuel cell operating conditions. Electrochim. Acta 53, 3279–3295 (2008).

    CAS  Google Scholar 

  26. 26.

    Gubler, L., Dockheer, S. M. & Koppenol, W. H. Radical (HO, H and HOO) formation and ionomer degradation in polymer electrolyte fuel cells. J. Electrochem. Soc. 158, B755–B769 (2011).

    CAS  Google Scholar 

  27. 27.

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

    CAS  Google Scholar 

  28. 28.

    Banham, D. et al. Critical advancements in achieving high power and stable nonprecious metal catalyst-based MEAs for real-world proton exchange membrane fuel cell applications. Sci. Adv. 4, eaar7180 (2018).

    PubMed  PubMed Central  Google Scholar 

  29. 29.

    Wang, X. X., Prabhakaran, V., He, Y. H., Shao, Y. Y. & Wu, G. Iron-free cathode catalysts for proton-exchange-membrane fuel cells: cobalt catalysts and the peroxide mitigation approach. Adv. Mater. 31, 1805126 (2019).

    Google Scholar 

  30. 30.

    Zitolo, A. et al. Identification of catalytic sites in cobalt–nitrogen–carbon materials for the oxygen reduction reaction. Nat. Commun. 8, 957 (2017).

    PubMed  PubMed Central  Google Scholar 

  31. 31.

    Sun, T. T. et al. Single-atomic cobalt sites embedded in hierarchically ordered porous nitrogen-doped carbon as a superior bifunctional electrocatalyst. Proc. Natl Acad. Sci. USA 115, 12692–12697 (2018).

    CAS  PubMed  Google Scholar 

  32. 32.

    Wang, X. X. et al. Nitrogen-coordinated single cobalt atom catalysts for oxygen reduction in proton exchange membrane fuel cells. Adv. Mater. 30, 1706758 (2018).

    Google Scholar 

  33. 33.

    Kattel, S., Atanassov, P. & Kiefer, B. Catalytic activity of Co–Nx/C electrocatalysts for oxygen reduction reaction: a density functional theory study. Phys. Chem. Chem. Phys. 15, 148–153 (2013).

    CAS  PubMed  Google Scholar 

  34. 34.

    He, Y. H. et al. Highly active atomically dispersed CoN4 fuel cell cathode catalysts derived from surfactant-assisted MOFs: carbon-shell confinement strategy. Energy Environ. Sci. 12, 250–260 (2019).

    CAS  Google Scholar 

  35. 35.

    Xiao, M. L. et al. Identification of binuclear Co2N5 active sites for oxygen reduction reaction with more than one magnitude higher activity than single atom CoN4 site. Nano Energy 46, 396–403 (2018).

    CAS  Google Scholar 

  36. 36.

    Wu, G., More, K. L., Johnston, C. M. & Zelenay, P. High-performance electrocatalysts for oxygen reduction derived from polyaniline, iron, and cobalt. Science 332, 443–447 (2011).

    CAS  PubMed  Google Scholar 

  37. 37.

    Song, J. Y. et al. Core–shell Co/CoNx@C nanoparticles enfolded by Co–N doped carbon nanosheets as a highly efficient electrocatalyst for oxygen reduction reaction. Carbon 138, 300–308 (2018).

    CAS  Google Scholar 

  38. 38.

    Cheng, Q. Q. et al. Co nanoparticle embedded in atomically-dispersed Co–N–C nanofibers for oxygen reduction with high activity and remarkable durability. Nano Energy 52, 485–493 (2018).

    CAS  Google Scholar 

  39. 39.

    Zhang, H. G., Osgood, H., Xie, X. H., Shao, Y. Y. & Wu, G. Engineering nanostructures of PGM-free oxygen-reduction catalysts using metal–organic frameworks. Nano Energy 31, 331–350 (2017).

    CAS  Google Scholar 

  40. 40.

    Park, K. S. et al. Exceptional chemical and thermal stability of zeolitic imidazolate frameworks. Proc. Natl Acad. Sci. USA 103, 10186–10191 (2006).

    CAS  PubMed  Google Scholar 

  41. 41.

    Yin, P. Q. et al. Single cobalt atoms with precise N-coordination as superior oxygen reduction reaction catalysts. Angew. Chem. Int. Ed. 55, 10800–10805 (2016).

    CAS  Google Scholar 

  42. 42.

    Hillman, F. et al. Rapid microwave-assisted synthesis of hybrid zeolitic–imidazolate frameworks with mixed metals and mixed linkers. J. Mater. Chem. A 5, 6090–6099 (2017).

    CAS  Google Scholar 

  43. 43.

    Strickland, K. et al. Highly active oxygen reduction non-platinum group metal electrocatalyst without direct metal–nitrogen coordination. Nat. Commun. 6, 7343–7351 (2015).

    CAS  PubMed  PubMed Central  Google Scholar 

  44. 44.

    Liedana, N., Galve, A., Rubio, C., Tellez, C. & Coronas, J. CAF@ZIF-8: one-step encapsulation of caffeine in MOF. ACS Appl. Mater. Inter. 4, 5016–5021 (2012).

    CAS  Google Scholar 

  45. 45.

    Lalancette, R. A., Syzdek, D., Grebowicz, J., Arslan, E. & Bernal, I. The thermal decomposition and analyses of metal tris-acetylacetonates. J. Therm. Anal. Calorim. 135, 3463–3470 (2019).

    CAS  Google Scholar 

  46. 46.

    Pan, F. P. et al. Unveiling active sites of CO2 reduction on nitrogen-coordinated and atomically dispersed iron and cobalt catalysts. ACS Catal. 8, 3116–3122 (2018).

    CAS  Google Scholar 

  47. 47.

    Swarbrick, J. C., Weng, T. C., Schulte, K., Khlobystov, A. N. & Glatzel, P. Electronic structure changes in cobalt phthalocyanine due to nanotube encapsulation probed using resonant inelastic X-ray scattering. Phys. Chem. Chem. Phys. 12, 9693–9699 (2010).

    CAS  PubMed  Google Scholar 

  48. 48.

    Fei, H. L. et al. General synthesis and definitive structural identification of MN4C4 single-atom catalysts with tunable electrocatalytic activities. Nat. Catal. 1, 63–72 (2018).

    CAS  Google Scholar 

  49. 49.

    Ziegelbauer, J. M. et al. Direct spectroscopic observation of the structural origin of peroxide generation from Co-based pyrolyzed porphyrins for ORR applications. J. Phys. Chem. C 112, 8839–8849 (2008).

    CAS  Google Scholar 

  50. 50.

    Lefevre, 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).

    CAS  PubMed  Google Scholar 

  51. 51.

    Jaouen, F., Lefevre, M., Dodelet, J. P. & Cai, M. Heat-treated Fe/N/C catalysts for O2 electroreduction: are active sites hosted in micropores? J. Phys. Chem. B 110, 5553–5558 (2006).

    CAS  PubMed  Google Scholar 

  52. 52.

    Kramm, U. I. et al. Structure of the catalytic sites in Fe/N/C-catalysts for O2-reduction in PEM fuel cells. Phys. Chem. Chem. Phys. 14, 11673–11688 (2012).

    CAS  PubMed  PubMed Central  Google Scholar 

  53. 53.

    Mineva, T. et al. Understanding active sites in pyrolyzed Fe–N–C catalysts for fuel cell cathodes by bridging density functional theory calculations and 57Fe Mössbauer spectroscopy. ACS Catal. 9, 9359–9371 (2019).

    CAS  Google Scholar 

  54. 54.

    The Hydrogen and Fuel Cell Technologies Office Multi-year Research, Development, and Demonstration Plan (US Department of Energy, 2017).

  55. 55.

    Uddin, A. et al. High power density platinum group metal-free cathodes for polymer electrolyte fuel cells. ACS Appl. Mater. Inter. 12, 2216–2224 (2020).

    CAS  Google Scholar 

  56. 56.

    Kinumoto, T. et al. Durability of perfluorinated ionomer membrane against hydrogen peroxide. J. Power Sources 158, 1222–1228 (2006).

    CAS  Google Scholar 

  57. 57.

    Goellner, V., Armel, V., Zitolo, A., Fonda, E. & Jaouen, F. Degradation by hydrogen peroxide of metal–nitrogen–carbon catalysts for oxygen reduction. J. Electrochem. Soc. 162, H403–H414 (2015).

    CAS  Google Scholar 

  58. 58.

    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 

  59. 59.

    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 

  60. 60.

    Ferrandon, M. et al. Stability of iron species in heat-treated polyaniline–iron–carbon polymer electrolyte fuel cell cathode catalysts. Electrochim. Acta 110, 282–291 (2013).

    CAS  Google Scholar 

  61. 61.

    Luo, J. H., Hong, Z. S., Chao, T. H. & Cheng, M. J. Quantum mechanical screening of metal-N4-functionalized graphenes for electrochemical anodic oxidation of light alkanes to oxygenates. J. Phys. Chem. C 123, 19033–19044 (2019).

    CAS  Google Scholar 

  62. 62.

    Ravel, B. & Newville, M. Athena, Artemis, Hephaestus: data analysis for X-ray absorption spectroscopy using IFEFFIT. J. Synchrotron Radiat. 12, 537–541 (2005).

    CAS  PubMed  Google Scholar 

  63. 63.

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

    CAS  Google Scholar 

  64. 64.

    Sun, G. Y. et al. Performance of the Vienna ab initio simulation package (VASP) in chemical applications. J. Mol. Struc. Theochem. 624, 37–45 (2003).

    CAS  Google Scholar 

  65. 65.

    Blochl, P. E. Projector augmented-wave method. Phys. Rev. B 50, 17953–17979 (1994).

    CAS  Google Scholar 

  66. 66.

    Kresse, G. & Joubert, D. From ultrasoft pseudopotentials to the projector augmented-wave method. Phys. Rev. B 59, 1758–1775 (1999).

    CAS  Google Scholar 

  67. 67.

    Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 78, 1396–1396 (1997).

    CAS  Google Scholar 

  68. 68.

    Ernzerhof, M. & Scuseria, G. E. Assessment of the Perdew–Burke–Ernzerhof exchange-correlation functional. J. Chem. Phys. 110, 5029–5036 (1999).

    CAS  Google Scholar 

  69. 69.

    Li, J. K., Alsudairi, A., Ma, Z. F., Mukerjee, S. & Jia, Q. Y. Asymmetric volcano trend in oxygen reduction activity of Pt and non-Pt catalysts: in situ identification of the site-blocking effect. J. Am. Chem. Soc. 139, 1384–1387 (2017).

    CAS  PubMed  Google Scholar 

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The authors acknowledge support from the US Department of Energy, Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office (DOE-EERE-HFTO) through the Electrocatalysis consortium (ElectroCat) and the DOE programme managers, D. Papageorgopoulos, S. Thompson, D. Peterson and G. Kleen. The XPS measurement was performed using EMSL(grid.436923.9), a DOE Office of Science user facility sponsored by the Biological and Environmental Research programme. PNNL is operated by Battelle for the US DOE under contract DE-AC05-76RLO1830. X-ray spectroscopy experiments were performed at MRCAT at the Advanced Photon Source (APS), a DOE Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under contract no. DE-AC02-06CH11357. The operation of MRCAT is supported both by DOE and the MRCAT member institutions. Argonne National Laboratory is operated for the US DOE by the University of Chicago Argonne LLC under contract no. DE-AC02-06CH11357. Electron microscopy was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. The DFT calculations were performed on the computers of the University of Pittsburgh Center for Research Computing as well as the Extreme Science and Engineering Discovery Environment (XSEDE), which is funded by National Science Foundation grant no. ACI-1053575.

Author information




X.X. and Y.S. formulated the concept. X.X. performed the synthesis and electrochemical tests. C.H. and V.R. performed the PEM fuel cell tests and analysed the data. Y.H. and X.S.L. conducted the Brunauer–Emmett–Teller and non-local DFT analyses, J.L. the thermogravimetric analysis, Z.N. and M.E.B. the PXRD analysis and T.L. the ICP-OES analysis. D.A.C. and M.S. performed the electron microscopy characterization. M.H.E. performed the XPS tests. E.C.W., A.J.K. and D.J.M. acquired and analysed the XAS data. G. Wang and B.L. performed the DFT calculations and analysed the results. Y.C. performed the Mössbauer measurements and analysed the data. U.M. and P.Z. performed the in situ CO2 emission tests and analysed the data. G. Wu provided guidance on catalyst design, synthesis and characterization. Y.S. supervised the research. X.X., Y.S., G. Wu, G. Wang, D.J.M. and P.Z. co-wrote the paper. All the authors discussed and commented on the manuscript. The views and opinions of the authors expressed here do not necessarily state or reflect those of the US government or any agency thereof. Neither the US government nor any agency thereof, nor any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness or usefulness of any information, apparatus, product or process disclosed, or represents that its use would not infringe privately owned rights.

Corresponding authors

Correspondence to Gang Wu, Vijay Ramani or Yuyan Shao.

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Competing interests

Battelle Memorial Institute has filed a USPTO provisional patent application (no. 62/985,713) on the Co–N–C catalyst and its synthesis reported in this paper; the inventors are Y.S. and X.X.; the status is provisional; and the title is ‘A High-Performing and Stable Platinum Group Metal (PGM) Catalyst for Fuel Cells’.

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Peer review information Nature Catalysis thanks Anatoly Frenkel and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Figs. 1–25, Tables 1–7, Discussions 1–4 and references.

Supplementary Data 1

Atomic coordinates of the optimized computational models.

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Xie, X., He, C., Li, B. et al. Performance enhancement and degradation mechanism identification of a single-atom Co–N–C catalyst for proton exchange membrane fuel cells. Nat Catal 3, 1044–1054 (2020).

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