Low-density phenyl content π-π stacking units based ionomers and membranes to improve power density for fuel-cells

Aryl ether-free aromatic polyelectrolytes featuring π-π stacking interaction exhibit remarkable conductivity and alkaline stability. This is attributed the formation of well-ordered ion-conducting channels and the prevention of backbone cleavage. However, the π-π stacking units usually consist of multiple phenyl groups. This characteristic results in significant adsorption of phenyl groups onto hydrogen oxidation catalysts, consequently impeding the performance of fuel cell. Herein, fluoranthene units with low phenyl content are employed in aryl ether-free backbones to prepare novel π-π stacking based anion exchange membranes (AEMs) and anion exchange ionomers (AEIs). The low-density phenyl content π-π stacking units effectively construct ion transport channels and weaken the phenyl group adsorption on hydrogen oxidation catalysts. The as-prepared polyelectrolyte works as AEI and AEM achieving both outstanding conductivity (143.69 mS/cm) and single cell performance (1.527 W/cm 2 ) at 80 °C. Furthermore, the membrane prepared in this study demonstrates outstanding mechanical strength (39.5 MPa) and alkaline stability. Specifically, it maintains 92 % of its initial conductivity after being exposed to 3 M KOH at 80 °C for 1000 h. This remarkable performance can be attributed to the rigid fluoranthene units and the aryl-ether-free backbones, which contribute to the membrane's structural integrity and resistance to degradation under alkaline conditions.