Synergistic tailoring of ether polybenzimidazole blend membranes with π-conjugated and flexible polymers for high temperature proton exchange fuel cells

Achieving simultaneous enhancement of proton conductivity and mechanical robustness remains a major challenge for phosphoric acid (PA) doped high temperature proton exchange membranes (HT-PEMs) in fuel cells. Here, ether-linked polybenzimidazole (OPBI) is blended with π-conjugated poly(dibenzothiophene ethylimidazole) (P(DBT-EIm)) and flexible polyethyleneimine (PEI) to investigate the effects of polymer structure on membrane performance. P(DBT-EIm) provides rigid π-conjugated backbones and dual PA-binding sites from nitrogen and sulfur atoms, enabling enhanced proton transport while maintaining structural stability. The resulted OPBI/P(DBT-EIm)-50 membrane with an acid doping content of 207% exhibits a high proton conductivity of 0.13 S cm −1 at 180 °C and a good tensile strength of 19.8 MPa at room temperature. A non-humidified H 2 /O 2 fuel cell delivers a peak power density of 861 mW cm −2 and a current density of 2446 mA cm −2 at 180 °C, with stable operation over current densities from 200 to 400 mA cm −2 .