Uneven Side-Chain Cation-Modified Poly(aryl piperidinium) Anion Exchange Membranes with Broadened OH– Conducting Channels for Fuel Cells

Although the anion exchange membranes (AEMs) prepared through superacid-catalyzed polymerization exhibit high alkaline stability, the hydrophobic microdomains in the AEMs impede OH– conduction. To fabricate AEMs with both high conductivity and alkaline stability, ether-free poly(aryl piperidine) is synthesized herein via superacid-catalyzed polymerization, which is then modified by the uneven side-chain cations simultaneously. The uneven side-chain cations possessing different lengths are advantageous for the dispersion of the cations, which can broaden OH– conducting channels. PAP-TP-Pip-50% membrane with the most uniform dispersion of cations possesses the highest water uptake (151.1%) and OH– conductivity (220.8 mS cm–1) at 80 °C among the prepared AEMs. The ether-free backbones and alkyl spacers, along with high water absorption caused by the broadened OH– conducting channels, endow PAP-TP-Pip-50% with excellent stability. After immersion in a 1 M NaOH solution (80 °C, 3000 h), the conductivity of PAP-TP-Pip-50% remains at 94.56% and PAP-TP-Pip-50% still possesses excellent mechanical properties. The single cell with PAP-TP-Pip-50% exhibits a peak power density of 1.77 W cm–2 (80 °C). After a 150 h endurance test, the voltage loss is just 94 mV. All these demonstrate that broadened OH– conducting channels through grafting uneven side-chain cations are an effective strategy for designing AEMs.