Triple-layer sulfonated poly(ether ether ketone)/sulfonated polyimide membranes for fuel cell applications

A series of triple-layer membranes were prepared based on a sulfonated polyimide (SPI) and a traditional sulfonated poly(ether ether ketone) (SPEEK) polymer matrix. Compared with the single-component membranes (pure SPI and SPEEK), the multicomponent membranes exhibited better comprehensive performance. Interestingly, the triple-layer membranes possessed improved mechanical properties, lower water uptake, and swelling ratio than those of the corresponding blend membranes. When the contents of SPI were 30 and 40%, the triple-layer membranes even had lower methanol permeability (3.42 and 2.61 × 10−7 cm2 s−1, respectively) than that of the pure SPI membrane (3.51 × 10−7 cm2 s−1). The proton conductivity of the triple-layer membranes was in the range of 0.117–0.149 S cm−1 at 100°C. All the results suggest that the triple-layer membranes have sufficiently excellent performance to be applied in fuel cells.