Anion exchange membrane fuel cells (AEMFCs) have been regarded as promising energy conversion devices for stationary and mobile applications due to their potentially low cost. To realize high-performance AEMFCs, new polymeric membranes are needed that are highly conductive and chemically stable. In this work, we synthesized a series of poly(2,6-dimethyl 1-4-phenylene oxide) (PPO)-based AEMs with different types of cationic side chains to study the relationship between the degree of functionalization (DF) and the structure of the side chain (charge number and charge arrangement) and the AEM performance in terms of ionic conductivity, swelling degree, and chemical stability of the material. When the spacers were chosen as 5 and/or 6 methylenes between charges, increasing the charge number of the cation side chain ensured higher IEC at low DF, which improved ion conduction and long-term stability. It was also observed that a triple-cation (three charges per cation side chain) AEM (TxNC6NC5N), exhibited higher conductivity and alkaline stability than that of single- (one charge per cation side chain, and SxNC6) and double-cation (two charges per cation side chain, DxN6N6) AEMs. The hydroxide ionic conductivity of T20NC6NC5N reached as high as 72 and 176 mS/cm at 25 and 80 °C, respectively. High conductivity was maintained during degradation under 1 M NaOH at 80 °C and did not significantly degrade (90% retention of conductivity after 21 days of degradation). Finally, based on the high-performance T20NC6NC5N sample, a H2/O2 AEMFC was assembled and tested. High polarization performance of the AEMFC with a peak power density of 364 mW/cm2 was achieved at 60 °C under 100% relative humidity. This talk will discuss details of how the degree of polymer backbone functionalization and arrangement of cations on the side chain impact AEM properties.

Multi-cation side chain anion-exchange membranes

251st National Meeting (2016)

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