Sandwich structure engineering for constructing proton exchange membranes with excellent stability and proton conductivity

It is a technical challenge to balance the proton conductivity and stability of proton exchange membranes (PEMs) due to the restriction of this trade-off relationship. To solve this issue, a novel sandwich structured PEM is fabricated, consisting of stable polybenzimidazole (PBI) layers on both sides of the highly hydrophilic sulfonated poly (aryl ether sulfone) (SPAES) layer in this work. Phosphotungstic acid (HPW) with strong intrinsic proton conductivity is chosen to add to the SPAES layer to further enhance the proton conductivity of the sandwich membranes. The introduction of high-stability PBI and the acid-base interaction between-NH-/-NH = groups present on PBI and the -SO3H groups on SPAES foster a crosslink-like network structure, which makes the sandwich membrane have superior thermal, size and mechanical stability, robust oxidative resistance, together with high HPW retention ability. By optimizing the doping amount of HPW and designing PBI with richer hydrogen bonding networks and stronger electron-withdrawing groups, higher through-plane proton conductivity has achieved. The SPAES+30%HPW/IPBI sandwich membrane particularly displays the through-plane proton conductivity of 162.1 mS/cm (90 degrees C), fuel cell output of 608.9 mW/cm2 and voltage loss of 0.30 mV/ h (80 degrees C), both superior to single-layer SPAES membrane. This indicates that the strategy of sandwich membranes provides a new research idea for designing stable and high proton conductivity PEMs.