Abstract
To achieve the US Department of Energy 2018 target set for platinum-group metal-free catalysts (PGM-free catalysts) in proton exchange membrane fuel cells, the low density of active sites must be overcome. Here, we report a class of concave Fe–N–C single-atom catalysts possessing an enhanced external surface area and mesoporosity that meets the 2018 PGM-free catalyst activity target, and a current density of 0.047 A cm–2 at 0.88 ViR-free under 1.0 bar H2–O2. This performance stems from the high density of active sites, which is realized through exposing inaccessible Fe–N4 moieties (that is, increasing their utilization) and enhancing the mass transport of the catalyst layer. Further, we establish structure–property correlations that provide a route for designing highly efficient PGM-free catalysts for practical application, achieving a power density of 1.18 W cm−2 under 2.5 bar H2–O2, and an activity of 129 mA cm−2 at 0.8 ViR-free under 1.0 bar H2–air.
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The data that support the plots within this paper and other findings of this study are available from the corresponding author on reasonable request.
References
Debe, M. K. Electrocatalyst approaches and challenges for automotive fuel cells. Nature 486, 43–51 (2012).
Shao, M., Chang, Q., Dodelet, J.-P. & Chenitz, R. Recent advances in electrocatalysts for oxygen reduction reaction. Chem. Rev. 116, 3594–3657 (2016).
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).
Gasteiger, H. A., Kocha, S. S., Sompalli, B. & Wagner, F. T. Activity benchmarks and requirements for Pt, Pt-alloy, and non-Pt oxygen reduction catalysts for PEMFCs. Appl. Catal. B 56, 9–35 (2005).
Chen, C. et al. Highly crystalline multimetallic nanoframes with three-dimensional electrocatalytic surfaces. Science 343, 1339–1343 (2014).
Bian, T. et al. Epitaxial growth of twinned Au–Pt core-shell star-shaped decahedra as highly durable electrocatalysts. Nano Lett. 15, 7808–7815 (2015).
Zhang, L., Wilkinson, D. P., Liu, Y. & Zhang, J. Progress in nanostructured (Fe or Co)/N/C non-noble metal electrocatalysts for fuel cell oxygen reduction reaction. Electrochim. Acta 262, 326–336 (2018).
Xia, B. Y. et al. A metal–organic framework-derived bifunctional oxygen electrocatalyst. Nat. Energy 1, 15006 (2016).
Zheng, Y. et al. Molecule-level g-C3N4 coordinated transition metals as a new class of electrocatalysts for oxygen electrode reactions. J. Am. Chem. Soc. 139, 3336–3339 (2017).
Wang, J. et al. Design of N-coordinated dual-metal sites: a stable and active Pt-free catalyst for acidic oxygen reduction reaction. J. Am. Chem. Soc. 139, 17281–17284 (2017).
Strickland, K. et al. Highly active oxygen reduction non-platinum group metal electrocatalyst without direct metal-nitrogen coordination. Nat. Commun. 6, 7343 (2015).
Multi-Year Research, Development, and Demonstration Plan (US Department of Energy, Fuel Cell Technologies Office, 2017).
Singh, K., Razmjooei, F. & Yu, J.-S. Active sites and factors influencing them for efficient oxygen reduction reaction in metal-N coordinated pyrolyzed and non-pyrolyzed catalysts: a review. J. Mater. Chem. A 5, 20095–20119 (2017).
Kramm, U. I., Lefèvre, M., Larouche, N., Schmeisser, D. & Dodelet, J.-P. Correlations between mass activity and physicochemical properties of Fe/N/C catalysts for the ORR in PEM fuel cell via 57Fe Mössbauer spectroscopy and other techniques. J. Am. Chem. Soc. 136, 978–985 (2014).
Zitolo, A. et al. Identification of catalytic sites for oxygen reduction in iron- and nitrogen-doped graphene materials. Nat. Mater. 14, 937–942 (2015).
Sahraie, N. R. et al. Quantifying the density and utilization of active sites in non-precious metal oxygen electroreduction catalysts. Nat. Commun. 6, 8618 (2015).
Li, J. et al. Structural and mechanistic basis for the high activity of Fe–N–C catalysts toward oxygen reduction. Energy Environ. Sci. 9, 2418–2432 (2016).
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).
Chen, Y. et al. Isolated single iron atoms anchored on N-doped porous carbon as an efficient electrocatalyst for the oxygen reduction reaction. Angew. Chem. Int. Ed. 56, 6937–6941 (2017).
Fei, H. et al. General synthesis and definitive structural identification of MN4C4 single-atom catalysts with tunable electrocatalytic activities. Nat. Catal. 1, 63–72 (2018).
Zhang, H. 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).
Chen, X., Yu, L., Wang, S., Deng, D. & Bao, X. Highly active and stable single iron site confined in graphene nanosheets for oxygen reduction reaction. Nano Energy 32, 353–358 (2017).
Liu, Q., Liu, X., Zheng, L. & Shui, J. The solid-phase synthesis of an Fe–N–C electrocatalyst for high-power proton-exchange membrane fuel cells. Angew. Chem. Int. Ed. 57, 1204–1208 (2018).
Wan, X. et al. Synthesis and active site identification of Fe−N−C single-atom catalysts for the oxygen reduction reaction. ChemElectroChem 6, 304–315 (2019).
Jaouen, F., Lefèvre, 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).
Ye, Y. et al. Surface functionalization of ZIF-8 with ammonium ferric citrate toward high exposure of Fe-N active sites for efficient oxygen and carbon dioxide electroreduction. Nano Energy 38, 281–289 (2017).
Fu, X. et al. In situ polymer graphenization ingrained with nanoporosity in a nitrogenous electrocatalyst boosting the performance of polymer-electrolyte-membrane fuel cells. Adv. Mater. 29, 1700363 (2017).
Pampel, J. & Fellinger, T.-P. Opening of bottleneck pores for the improvement of nitrogen doped carbon electrocatalysts. Adv. Energy Mater. 6, 1502389 (2016).
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).
O’Hayre, R., Barnett, D. M. & Prinz, F. B. The triple phase boundary a mathematical model and experimental investigations for fuel cells. J. Electrochem. Soc. 152, A439 (2005).
Seh, Z. W. et al. Combining theory and experiment in electrocatalysis: insights into materials design. Science 355, eaad4998 (2017).
Proietti, E. et al. Iron-based cathode catalyst with enhanced power density in polymer electrolyte membrane fuel cells. Nat. Commun. 2, 416 (2011).
Antonacci, P. et al. Balancing mass transport resistance and membrane resistance when tailoring microporous layer thickness for polymer electrolyte membrane fuel cells operating at high current densities. Electrochim. Acta 188, 888–897 (2016).
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).
Zeng, X. et al. Single-atom to single-atom grafting of Pt1 onto Fe–N4 center: Pt1@Fe–N–C multifunctional electrocatalyst with significantly enhanced properties. Adv. Energy Mater. 8, 1701345 (2018).
Charreteur, F., Ruggeri, S., Jaouen, F. & Dodelet, J. P. Increasing the activity of Fe/N/C catalysts in PEM fuel cell cathodes using carbon blacks with a high-disordered carbon content. Electrochim. Acta 53, 6881–6889 (2008).
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).
Meng, H. et al. Iron porphyrin-based cathode catalysts for polymer electrolyte membrane fuel cells: effect of NH3 and Ar mixtures as pyrolysis gases on catalytic activity and stability. Electrochim. Acta 55, 6450–6461 (2010).
Jaouen, F. et al. Oxygen reduction activities compared in rotating-disk electrode and proton exchange membrane fuel cells for highly active Fe–N–C catalysts. Electrochim. Acta 87, 619–628 (2013).
Afsahi, F. & Kaliaguine, S. Non-precious electrocatalysts synthesized from metal–organic frameworks. J. Mater. Chem. A 2, 12270 (2014).
Zhu, Q.-L., Xia, W., Akita, T., Zou, R. & Xu, Q. Metal-organic framework-derived honeycomb-like open porous nanostructures as precious-metal-free catalysts for highly efficient oxygen electroreduction. Adv. Mater. 28, 6391–6398 (2016).
Shui, J., Chen, C., Grabstanowicz, L., Zhao, D. & Liu, D.-J. Highly efficient nonprecious metal catalyst prepared with metal-organic framework in a continuous carbon nanofibrous network. Proc. Natl Acad. Sci. USA 112, 10629–10634 (2015).
Armel, V. et al. Structural descriptors of zeolitic-imidazolate frameworks are keys to the activity of Fe–N–C catalysts. J. Am. Chem. Soc. 139, 453–464 (2016).
Zhou, B. et al. Ferrocene-based porous organic polymer derived high-performance electrocatalysts for oxygen reduction. J. Mater. Chem. A 5, 22163–22169 (2017).
Zhao, D. et al. Highly efficient non-precious metal electrocatalysts prepared from one-pot synthesized zeolitic imidazolate frameworks. Adv. Mater. 26, 1093–1097 (2014).
Tian, J. et al. Optimized synthesis of Fe/N/C cathode catalysts for PEM fuel cells: a matter of iron-ligand coordination strength. Angew. Chem. Int. Ed. 52, 6867–6870 (2013).
Zhao, D. et al. Iron imidazolate framework as precursor for electrocatalysts in polymer electrolyte membrane fuel cells. Chem. Sci. 3, 3200–3205 (2012).
Yuan, S. et al. A highly active and support-free oxygen reduction catalyst prepared from ultrahigh-surface-area porous polyporphyrin. Angew. Chem. Int. Ed. 52, 8349–8533 (2013).
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).
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).
He, Y. 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).
Li, J. et al. Atomically dispersed manganese catalysts for oxygen reduction in proton-exchange membrane fuel cells. Nat. Catal. 1, 935–945 (2018).
Shang, L. et al. Well-dispersed ZIF-derived Co,N-co-doped carbon nanoframes through mesoporous-silica-protected calcination as efficient oxygen reduction electrocatalysts. Adv. Mater. 28, 1668–1674 (2016).
Gor, G. Y., Thommes, M., Cychosz, K. A. & Neimark, A. V. Quenched solid density functional theory method for characterization of mesoporous carbons by nitrogen adsorption. Carbon 50, 1583–1590 (2012).
Newville, M. IFEFFIT: interactive XAFS analysis and FEFF fitting. J. Synchrotron Radiat. 8, 322–324 (2001).
Ravel, B. & Newville, M. ATHENA, ARTEMIS, HEPHAESTUS: data analysis for X-ray absorption spectroscopy using IFEFFIT. J. Synchrotron Radiat. 12, 537–541 (2005).
Acknowledgements
This work was supported by the National Thousand Talents Plan of China, the National Natural Science Foundation of China (grant no. 21673014), the 111 project (B17002) funded by the Ministry of Education of China and the Fundamental Research Funds for the Central Universities of China. The authors thank D. N. Futaba (AIST, Japan) for language polishing.
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X.W. and J.S. conceived the idea. X.W. performed the synthesis, electrochemical tests and characterizations. H.W. performed TEM characterizations. X.L. performed XAS measurement and analysis. L.Z. and W.Y provided expertise for XAS analysis. Y.L. provided the structural models for XAS analysis. R.Y. and J.S. supervised the project and participated in the planning of research. X.W., X.L., M.X. and J.S. co-wrote the paper. All authors discussed the results and commented on the manuscript.
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Wan, X., Liu, X., Li, Y. 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). https://doi.org/10.1038/s41929-019-0237-3
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DOI: https://doi.org/10.1038/s41929-019-0237-3