Highly-conductive proton exchange membrane of sulfonated poly(biphenyl alkylene) copolymers for H2/O2 fuel cell with 2.62 W cm-2 power density

Ether-free proton exchange membranes (PEMs) based on aromatic polymers are considered as potential alternatives to perfluorosulfonic acid (PFSA) PEMs due to their low cost, less reactant crossing, exceptional chemical stability and outstanding thermal stability. Herein, a series of high-performance sulfonated poly(biphenyl alkylene) (BPSA-PT-x) membranes with full carbon chain backbones were synthesized to investigate the effect of different ratios of hydrophobic components on membrane properties. Among the prepared membranes, the BPSA-PT-10 % PEM with the highest proton conductivity (311 mS cm-1 at 80 °C water) possessed excellent dimensional stability (in-plane swelling rate ≤19.7 %, through-plane swelling rate ≤24.9 %), mechanical properties (elongation at break: 89.8 % in wet state), thermal stability (glass transition temperature >450 °C) and low H2 crossover (1.80 mA cm-2). Further, the assembled H2/O2 fuel cell based on BPSA-PT-10 % PEM exhibited competitive performance with a peak power density of 2.62 W cm-2. The developed poly(biphenyl alkylene)-based PEMs should have potential applications in hydrogen energy field.