One promising approach to reduce the cost of fuel cell systems is to develop hydroxide exchange membrane fuel cells (HEMFCs), which open up the possibility of platinum-group-metal-free catalysts and low-cost bipolar plates. However, scalable alkaline polyelectrolytes (hydroxide exchange membranes and hydroxide exchange ionomers), a key component of HEMFCs, with desired properties are currently unavailable, which presents a major barrier to the development of HEMFCs. Here we show hydroxide exchange membranes and hydroxide exchange ionomers based on poly(aryl piperidinium) (PAP) that simultaneously possess adequate ionic conductivity, chemical stability, mechanical robustness, gas separation and selective solubility. These properties originate from the combination of the piperidinium cation and the rigid ether-bond-free aryl backbone. A low-Pt membrane electrode assembly with a Ag-based cathode using PAP materials showed an excellent peak power density of 920 mW cm−2 and operated stably at a constant current density of 500 mA cm−2 for 300 h with H2/CO2-free air at 95 °C.

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This material is based upon work supported by the by the US Department of Energy, Advanced Research Projects Agency-Energy under Award No. DE-AR0000771. We thank Z. Green and H. Xu at Giner for performing the gas crossover measurement. We also thank R. Ma, J. Nash, J. A. Wittkopf and M. D. Woodroof for their assistance in the durability test of H2/O2 HEMFCs.

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  1. These authors contributed equally: Junhua Wang and Yun Zhao.


  1. Centre for Catalytic Science and Technology, Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE, USA

    • Junhua Wang
    • , Yun Zhao
    • , Brian P. Setzler
    • , Santiago Rojas-Carbonell
    • , Lan Wang
    • , Keda Hu
    • , Lin Shi
    • , Shimshon Gottesfeld
    • , Bingjun Xu
    •  & Yushan Yan
  2. Elbit Systems Ltd, Caesarea Business and Industrial Park, Caesarea, Israel

    • Chaya Ben Yehuda
    • , Alina Amel
    •  & Miles Page


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J.W. synthesized the polymers, fabricated the membranes, and performed the characterizations of polymers and membranes. Y.Z. prepared MEAs with Pt electrodes and tested their H2/O2 performance and durability. B.P.S. measured the electronic area specific resistance and stability of the membrane under RH cycling and pressure differential. S.R.-C. and L.S. developed the casting process for fabricating the large membranes. C.B.Y., A.A. and M.P. prepared MEAs with Ag cathodes and low-Pt anodes and tested their H2/CO2-free air performance and durability. L.W. performed the thermal analysis for the membranes. K.H. measured the polymer molecular weight. S.G. provided guidance in the development and testing of H2/CO2-free air MEAs. J.W., Y.Z., B.X. and Y.Y. conceived the ideas and wrote the manuscript with support from other coauthors.

Competing interests

C.B.Y, A.A. and M.P. are employed by Elbit Systems Ltd, which is a company specializing in fuel cells.

Corresponding authors

Correspondence to Bingjun Xu or Yushan Yan.

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