Achieving High‐Performance and 2000 h Stability in Anion Exchange Membrane Fuel Cells by Manipulating Ionomer Properties and Electrode Optimization

The primary function of the ionomers that are incorporated into fuel cell electrode catalyst layers is to provide pathways for ion transport between the catalyst active sites and the electrolyte. This is influenced by many variables, including the ion‐exchange capacity, water uptake, and molecular weight. In anion exchange membrane fuel cells (AEMFCs), controlling ionomer water uptake is particularly important and tailoring this property in each electrode is an important consideration when looking to maximize cell performance. In this study, three poly(norbornene) tetrablock copolymer ionomers with a range of physical properties are synthesized and incorporated into AEMFC anode and cathode electrodes. Systematic electrode engineering with these ionomers allows the peak power density to be increased by 100% (1.6 W cm‐2 → 3.2 W cm‐2) and the current density at 0.2 V to be increased by 59% (5.9 A cm‐2 → 9.4 A cm‐2). Moreover, the top‐performing electrode configuration is tested in an operating AEMFC at the US Department of Energy defined current density of 600 mA cm‐2 for 2000 h, showing a record‐low voltage decay rate of 15.36 µV h‐1 – only 3.65% –a over 2000 h. This work sets a new bar for AEMFCs, reporting the best combination of performance and durability of any AEMFC to date. Poly(norbornene) tetrablock copolymer ionomers with a range of physical properties are synthesized. This results in ionomers with varied water uptake and water transport properties. The ionomers are incorporated into anode and cathode electrodes of anion exchange membrane fuel cells. The electrode composition is optimized, including adding hydrophobic polytetrafluoroethylene. The result is very high fuel cell performance and record lifetime.