Chemically stable poly(meta-terphenyl piperidinium) with highly conductive side chain for alkaline fuel cell membranes

Abstract

Poly(arylene piperidine)s (PAPs) backbones, which do not contain unstable ether bonds, was synthesized by one-pot, metal-free superacid-catalyzed polymerization for anion exchange membranes (AEMs) preparation. Meta-terphenyl as a monomer of polymer to regulate the morphology and properties of AEM was also used due to its spatially torsional configuration instead of the recently reported linear structure of peta-terphenyl. Long flexible hydrophilic chains were grafted onto poly(meta terphenyl piperidinium) (m-PTP) backbone to form four cationic functionalized side chains, promoting efficient transfer of OH− and optimizing the hydrophilic/hydrophobic microphase separation structure. The resulting AEM shows a high ion conductivity of 164 mS/cm (m-PTP-TFPE-21) at 80 °C. Furthermore, stable piperidine cation and long alkyl spacer chain contributed to the excellent alkali stability of m-PTP-TFPE-TQA membrane which shows only 11.67% and 12.73% degradation in ion conductivity and IEC, respectively, after soaking in 2 M NaOH at 80 °C for 1500 h. The peak power density of the H2/O2 single cell using m-PTP-TFPE-14 is 269 mW/cm2 at a current density of 540 mA/cm2 at 80 °C.