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.
Supplementary Figures 1–13, Supplementary Tables 1–2