Enhancing Hydroxide Conductivity and Stability of Anion Exchange Membrane by Blending Quaternary Ammonium Functionalized Polymers

Abstract In this study, a well-designed polysulfone with dense phenyl groups surrounding its backbone (designated as P(ES1-co-ES2)) was synthesized and then modified with abundant quaternary ammoniums (QA). The QA functionalized P(ES1-co-ES2) was added to QA functionalized poly (ether ether ketone) with N,N,N',N'-tetramethyl-1,6-hexanediamine (TMHDA) as crosslinking reagent to fabricate anion exchange imembranes (AEM). The incorporation of abundant QA groups substantially increased the ion exchange capacity of the blend membranes. Meanwhile, the densely QA functionalized P(ES1-co-ES2) acted as “hydroxide ion wires” in blend membranes, constructing efficient ion channels for high-speed ion transfer. High hydroxide conductivity up to 215.4 mS cm−1 at 90 °C and the maximum power density of single fuel cell up to 137.2 mW cm−2 at 60 °C were thus achieved. In addition, the strong covalent interaction caused by TMHDA led to significantly enhanced physical stability (anti-swelling, tensile strength and elongation etc.), while the steric hindrance by the long aliphatic chain of TMHDA enhanced the chemical stability of the blend membranes. This study presents a novel AEM with simultaneously enhanced hydroxide conductivity, physical and chemical stabilities.