Multi‐arm Branched Poly(carbazole‐aryl piperidinium) Anion Exchange Membrane with High Conductivity and Good Alkaline Stability for Fuel Cells

Comprehensive Summary The lack of anion exchange membranes (AEMs) with good conductivity and alkaline stability has been one of the challenges for alkaline fuel cells. Introducing branched structure was a good strategy to promote conductivity and alkaline stability due to the bigger free volume of polymer and steric hindrance of cation. Herein, a series of branched AEMs with multiple arms (four and six) were successfully prepared. Multi‐arm branched AEMs demonstrated obvious improvement of conductivity and alkaline stability because of the larger free volume and steric hindrance of multi‐arm branched structures, respectively. Four‐arm branched B4‐QPPCTP‐5 exhibited best comprehensive performance, including high conductivity of 242.2 mS·cm –1 , a good alkaline stability of 2000 h with hardly degradation, and high mechanical property of >40 MPa. Single fuel cell based on multi‐arm branched AEMs exhibited high power output of 1.2 W·cm –2 . This work provides effective theoretical guidance for polymer structure design and preparation of branched AEMs.