Proton exchange membrane deriving from sulfonated N-heterocyclic poly(aryl ether ketone)s containing ether-free proton conducting units and performing enhanced physicochemical stability and conduction properties

Abstract

Sulfonated aromatic polymer proton exchange membranes suffer from the trade-off relationship between physicochemical stability and proton conductivity hampering the membrane application in fuel cells. To bridge the effect, the high-performance membranes exhibiting excellent proton conduction behavior and good stability are constructed from sulfonated N-heterocyclic poly(aryl ether)s designed elaborately, in which the hydrophilic units are constructed by combining the high-density pendant benzenesulfonic groups and biphthalazindione structures without the introduction of weak linkage units like ether bonds. The twisted heterocyclic structures and the multiple interactions between heterocyclic structures and sulfonic groups enhance the physical stability and proton-conduction behavior with the highest conductivity of 256 mS cm−1 for the membranes. The membranes perform rupture time between 3.9 and 7.1 h in high temperature Fenton's oxidation test, exhibiting good chemical stability. The cells loading the membranes perform the maximum power density between 1.08 and 2.30 W cm−2. The above results verify the benefits of constructing ether-free heterocyclic hydrophilic units with high-density proton-conducting groups for the improvement of comprehensive membrane performance.