Multilayered hydrocarbon ionomer/PTFE composite electrolytes with enhanced performance for energy conversion devices

A new multilayered composite membrane was prepared by impregnating a sulfonated poly(arylene ether sulfone) (SPAES) ionomer into a porous polytetrafluoroethylene (PTFE) substrate for application in proton exchange membrane fuel cells (PEMFCs) and water electrolyzers (PEMWEs). The PTFE substrate was treated with n-propyl alcohol to mediate the interfacial interactions between the SPAES solution and PTFE. Using the 10- and 5-μm-thick PTFE substrates, three-layered and five-layered composite membranes were prepared, respectively, to investigate the effect of PTFE thickness on impregnation of the SPAES ionomer. When 5-μm-thick PTFE was applied, the SPAES ionomer was effectively impregnated without noticeable defects, indicating a strong interlocking structure between the two incompatible components. Therefore, the five-layered composite membrane showed enhanced dimensional stability and mechanical properties compared to the SPAES membrane, and the effect of the PTFE on proton conductivity was minimized. Consequently, the cell performances of the five-layered composite membrane were reflected by current densities of 1.71 A/cm² at 0.5 V and 9.76 A/cm² at 1.9 V for PEMFC and PEMWE, respectively, corresponding to 44% and 32% increases compared to those of Nafion 212, owing to its smaller membrane resistance. Moreover, the prepared composite membrane presented excellent durability, which resulted in stable wet-dry cyclability and low degradation rates.