Preparation and fuel cell performance of carbonyl and sulfone groups co-crosslinked sulfonated polyimide proton exchange membranes

A series of six-membered ring type SPI PEMs was synthesized with 3,5-bis(4-aminophenoxy) benzoic acid(BAPBa). Carbonyl and sulfone co-crosslinked SPI PEMs were prepared by methanesulfonic acid/phosphorus pentoxide solution(PPMA). Their properties including proton conductivity, hydrolysis resistance, mechanical properties and fuel cell performance were investigated. The results showed that the crosslinking degree of carbonyl and sulfone co-crosslinked SPI PEMs increased, while the consumption of sulfonic acid group decreased, which kept the SPI PEMs maintaining high proton conductivity when compared to the sulfone groups crosslinked ones. For example, the proton conductivity of the carbonyl and sulfone co-crosslinked SPI PEM was 7.8 mS/cm at 50%RH, which increased by 28%. After aging in water at 130 ℃ for 500 h, elongation at break of the carbonyl and sulfone co-crosslinked SPI PEM was 18% and no obvious reduction in proton conductivity. Fuel cell performance showed that, the maximum power output of the carbonyl and sulfone co-crosslinked SPI PEM reached 0.85 W/cm², which was 1.3 times higher than that of sulfone crosslinked one.