Improving fuel cell performance of an anion exchange membrane by terminal pending bis-cations on a flexible side chain

Alkaline fuel cell devices which convert chemical energy into electrical energy largely rely on the alkaline anion (OH−) conductive capacity of the central component (anion exchange membrane (AEM)). A well-known strategy to improve the OH− conductivity is to construct ion channels inside the AEM for fast ion transport, instead of commonly increasing content of ionic units which is likely to cause excessive water swelling. This study presents a polymer concept of pending bis-cationic head groups onto the polymer backbone by a long flexible spacer. The triazole-containing spacer apart the terminal bis-cations far away from the backbone, thus providing benefits of enhanced OH− conductivity and mitigated water swelling. Small angle X-ray scattering (SAXS) analysis demonstrates a well-defined nano-phase separated morphology due to facilitated self-assembling behavior of the ionic side-chains. A H2/O2 single-cell fuel cell containing the resulting NPPO-2QA-1.85 AEM exhibits a peak power density of 310 mW cm-2, which is competitive among the recently reported for comparable multi-cations side-chain type AEM. [Display omitted] •Anion exchange membranes with bis-cations terminated side chains were synthesized.•The chemical structures of resulting polymers were well characterized and controlled.•Distinct ion conducting channel with an average size of 6.3 nm was confirmed.•The resulting membrane exhibits a H2/O2 fuel cell peak power density of 310 mW cm-2 at 80 oC.