Phosphoric acid-doped cross-linked poly(phenylene oxide)-based membranes for high temperature proton exchange membrane fuel cells

In this study, a series of cross-linked poly (phenylene oxide) (PPO)-based membranes with and without rotatable ethylene oxide spacers are prepared. Both PPO-based membranes possess good thermal stability, excellent oxidative stability, and satisfactory dimensional stability in phosphoric acid (PA) owing to their cross-linked structure and PPO backbone. The cross-linked PPO-based membrane with a rotatable ethylene oxide spacer exhibits enhanced conductivity, higher tensile strength, and better oxidative stability compared with that without the rotatable spacer. Owing to a better trade-off effect, the cross-linked membrane with the rotatable ethylene spacer exhibits higher H2/air cell performance (maximum power density, 237 mW cm−2) than that without the rotatable spacer (maximum power density, 144 mW cm−2). The introduction of rotatable spacers is an effective method for enhancing the performance of high-temperature proton exchange membranes.