Partially PEG-Grafted Poly(Terphenyl Piperidinium) Anion Exchange Membranes with Balanced Properties for Alkaline Fuel Cells

Poly(ethylene glycol) (PEG) or oligo (ethylene glycol) (OEG) grafted anion exchange membranes (AEMs) exhibit improved ionic conductivity, high alkaline stability, and subsequent boosted AEM fuel cell performance, but too much PEG/OEG side chains may can result in a reduction in the ion exchange capacity (IEC), which can have adverse effects on ion transport. Here, a series of partially PEG-grafted poly(terphenyl piperidinium) with different side chain length are synthesized using simple postpolymerization modification to produce AEMs with balanced properties. The polar and flexible PEG side chains are responsible for the controlled water uptake and swelling, superior hydroxide conductivity (122 mS cm-1 at 80 degrees C with an IEC of 1.99 mmol g-1), and enhanced alkaline stability compared to the reference sample without PEG grafts (PTP). More importantly, the performance of AEM fuel cell (AEMFC) with the membrane containing partial PEG side chains surpasses that with PTP membrane, demonstrating a highest peak power density of 1110 mW cm-2 at 80 degrees C under optimized conditions. This work provides a novel approach to the fabrication of high-performance AEM materials with balanced properties for alkaline fuel cell application. In this study, flexible PEG side chains with different length are partially attached onto poly(terphenyl piperidinium) to balance the performance of AEMs. The resulting membranes show controlled water uptake, high IEC-normalized conductivity, robust mechanical strength, and improved alkaline stability as compared to PTP and PTP-PEG-350 counterparts, yielding an excellent peak power density up to 1110 mW cm-2 in AEMFCs. image