Highly conductive branched poly(aryl piperidinium) anion exchange membranes with robust chemical stability

Poly(aryl piperidinium) (PAP) anion exchange membranes (AEMs) furnish an important avenue for the commercialization of anion exchange membrane fuel cells (AEMFCs), but their ionic conductivity and alkali resistance still need to be improved. Here, we report the synthesis of PAP AEMs with a branched structure by the acid-catalyzed reaction and compare them with the main-chain AEMs. The experimental results show that the branched AEMs have higher OH^- conductivity and alkaline resistance than the poly(terphenyl piperidine) (PTPQ1) AEM. The alkaline stability and OH^- conductivity of the AEMs were further improved by a flexible multi-cation crosslinker. The results show that the branched poly(p-terphenyl triphenylmethane 1-methyl piperidine) membrane crosslinked by multi-cation (PTTPQ4-40) shows an excellent OH^- conductivity (155.3 mS cm^-1) at 80 °C. The OH^- conductivity of the PTTPQ4-40 membrane was maintained at 92.1% after soaking in 2 M NaOH for 1080 h at 80 °C. In addition, the peak power density (PPD) of the crosslinked PTTPQ4-40 membrane can reach 656.7 mW cm^-2. Compared to the PTPQ1 AEM, the PPD of the crosslinked PTTPQ4-40 AEM is increased by 38.6% in H₂-O₂. All of the results confirm that the PTTPQ4-40 AEM has excellent fuel cell application prospects.