A facile approach to fabricate poly(2,6-dimethyl-1,4-phenylene oxide) based anion exchange membranes with extended alkaline stability and ion conductivity for fuel cell applications

Abstract

An effective strategy to improve both the conductivity and alkaline stability of anion exchange membranes (AEMs) was proposed by incorporating quaternary ammonium functionalized polyhedral oligomeric silses-quioxane (QPOSS) into quaternized poly(2,6-dimethyl-1,4-phenylene oxide) (QPPO). Glycidyltrimethylammonium chloride (GTMAC) was used as the main quaternized reagent for the synthesis of QPOSS. The introduction of QPOSS provided the hybrid membranes with additional ion hopping sites and ion conducting channels. The QPPO-QPOSS membrane with high ion exchange capacity of 4.81 meq g(-1) possessed the hydroxide ion conductivity of 8.77 x 10(-2) Scm(-1) at 80 degrees C. Meanwhile, the hybrid composite membranes showed enhanced alkaline stability due to the steric hindrance offered by QPPO and QPOSS and good alkaline resistance of long alkyl chain from octaammonium and glycidyl trimethyl ammonium bulky substituents. The residual ratio of hydroxide conductivity of QPPO-QPOSS-3 after being treated with 1 M KOH at room temperature for 1200 h reached 102%. The improved interfacial compatibility among the matrix polymer and filler imparted the hybrid membranes enhanced mechanical properties, good dimensional and thermal stability. The H-2/O-2 fuel cell using composite membrane of 3 wt% QPOSS relative to QPPO reached a maximum power density of about 288 mWcm(-2). The prepared hybrid membrane with promising characteristics exhibited the potential for applications in alkaline anion exchange membrane fuel cells in considering their integrative properties.