Advanced performance and ultra-high, long-term durability of acid-base blended membranes over 900 hours containing sulfonated PEEK and quaternized poly(arylene ether sulfone) in H₂/O₂ fuel cells

In this study, quaternized poly (arylene ether sulfone) (QNPAES) was synthesized using conventional nucleophilic aromatic polycondensation. We then developed a blended membrane composed of sulfonated poly (ether ether ketone) (SPEEK) using facile solution casting. A series of mixed hybrid membranes of SPEEK/QNPAES were prepared by varying the wt% of QNPAES mixed with SPEEK. The results showed that an appropriate amount of QNPAES (i.e., 6 wt%) could significantly improve the mechanical strength, proton conductivity and physicochemical properties of a prepared mixed membrane, as well as the proton exchange membrane fuel cell (PEMFC) performance and durability at relative humidity (RH) of 20%. Specifically, a SPEEK/QNPAES at 6 wt% provides a current output, power output and endurance of 0.431 A cm⁻², 0.15 W cm⁻² and over 900 h, respectively, at an RH of 20% and 60 °C. These results can be attributed to acid-base ionic crosslinking, which offers effective interfacial compatibility between SPEEK and QNPAES. A PEMFC with SPEEK/QNPAES membranes when used at 20% RH achieved significantly advanced performance and ultra-high, long-term durability compared with those of PEMFCs with bare SPEEK, suggesting that SPEEK/QNPAES membranes can be used as polymer electrolyte membranes.