Enhanced Stability of Quaternary Ammonium Cross‐Linked SEBS Anion Exchange Membranes for Fuel Cells

Abstract A novel alkaline anion exchange membrane was designed using poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene) (SEBS) as the backbone. Long side chains were grafted onto SEBS via a Friedel‐Crafts reaction, and a cross‐linked membrane (SEBS‐C6‐DiPRD) was prepared using an N‐heterocyclic crosslinker, 1,3‐N‐4‐piperidinyl propane, which features ring strain and steric hindrance. The prepared SEBS‐C6‐DiPRD membrane exhibited an ion exchange capacity of approximately 1.8 mmol·g −1 , a water uptake of 85.4%, and a swelling ratio of 24.1% at 80 °C. Thermal degradation began at 370 °C, and the membrane broke at a strain of 310.6% and a stress of 31.1 MPa. At the operating temperature of 80 °C (typical for AEMFCs), the conductivity reached 75.95 mS·cm −1 . Notably, after 1000 hours of testing under simulated AEMFC conditions, the membrane's conductivity only decreased by 27.6%, demonstrating excellent long‐term stability. Under H 2 and air conditions, the peak power density of the SEBS‐C6‐DiPRD membrane was 18.89 mW·cm −2 .