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Magnetic-field-oriented mixed-valence-stabilized ferrocenium anion-exchange membranes for fuel cells

Abstract

Through-plane (TP) conducting pathways in anion-exchange membranes (AEMs) are desirable for AEM fuel cells as they serve as short and efficient routes for hydroxide ion transport between electrodes, improving power output. Electric and magnetic fields have previously been used to create TP-oriented structures in AEMs, but with modest performance gains. Here we use paramagnetic ferrocenium polymers to prepare TP-oriented AEMs under a magnetic field. The magnetic field induces a mixed-valence state, which effectuates higher anion dissociation and enhanced alkali/redox stability. Our AEMs display a promising TP hydroxide conductivity of ~160 mS cm−1 at 95 °C in water, and no appreciable hydroxide conductivity loss over 4,320 h at 95 °C in alkali. The assembled fuel cells achieve a power output of 737 mW cm−2 at 80 °C and 80% relative humidity, and a durability of 3.9% voltage loss and 2.2% high-frequency resistance increase over 500 h at 500 mA cm−2, 120 °C and 40% relative humidity.

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Fig. 1: Syntheses of PF-OH and LPF-OH.
Fig. 2: Visual appearance and spectroscopic analyses of polymer and membrane samples.
Fig. 3: Membrane characterization.
Fig. 4: Membrane conductivity and stability.
Fig. 5: AEMFC evaluation.

Data availability

The authors declare that all data supporting the findings of this study are available within the paper and its Supplementary Information. Source data are provided with this paper.

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Acknowledgements

The authors thank the National Natural Science Foundation of China (21875161 and 22005214). The authors also thank the National Key Technology R&D Program (2018YFB0105601), the Natural Science Foundation of Tianjin (17JCZDJC31000) and the State Key Laboratory of Engines for financial support. A portion of this work was performed on the Steady High Magnetic Field Facilities (SM1 superconducting magnet), High Magnetic Field Laboratory, Chinese Academy of Sciences (Hefei, China). The authors thank researcher Jun Fang at the High Magnetic Field Laboratory for operating the SM1 superconducting magnet during the membrane casting process. D.R.D would like to thank the financial support of the Nancy & Stephen Grand Technion Energy Program (GTEP), and of Planning & Budgeting Committee / ISRAEL Council for Higher Education (CHE) and Fuel Choice Initiative (Prime Minister Office of ISRAEL) within the framework of “Israel National Research Center for Electrochemical Propulsion (INREP)”.

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M.D.G. and X.L. conceived the study. M.D.G. and X.L. designed the experiments. M.D.G., D.R.D., Y.Y., J.Z. and X.L. wrote the manuscript. X.L., N.X., J.X., M.L. and C.Z. carried out the experiments and collected the data. X.L., N.X. M.L. and C.Z. prepared the data graphs. M.D.G., D.R.D., Y.Y., J.Z., Y.Q. and X.L. discussed the results. All authors commented on the manuscript.

Corresponding authors

Correspondence to Yan Yin or Michael D. Guiver.

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Nature Energy thanks Christopher Arges, Patric Jannasch and Pawel Majewski for their contribution to the peer review of this work.

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Supplementary Figures 1–11, Notes 1–7, Tables 1–16 and Refs. 1–69

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Liu, X., Xie, N., Xue, J. et al. Magnetic-field-oriented mixed-valence-stabilized ferrocenium anion-exchange membranes for fuel cells. Nat Energy 7, 329–339 (2022). https://doi.org/10.1038/s41560-022-00978-y

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