Tailoring of microporosity of Tröger's base (TB) high temperature proton exchange membrane by miscible polymer blending

To further mitigate the phosphoric acid leakage in high temperature proton exchange membrane (PEM), the microporosity of Tröger's base (TB) membrane based on a V-shaped bridged bicyclic diamine has been fine-tailored readily by polymeric blending with a miscible polymer of intrinsic microporosity (PIM-1). As expected, the average cavity radius in the range of 3.46–4.21 Å has been achieved when the blending ratio of PIM-1 increases from 5 to 20 mol% due to the interaction between the amine group of TB and the nitrile group of PIM-1. The resulting PEMs show excellent PA retention ability. Notably, PIM/TB9 membrane with a suitable cavity radius of 3.5 Å and largest FFV4 of 49.1% exhibits an exciting PA retention of about 80%, which is much better than the pristine TB membrane. Thus, the remaining proton conductivity of PIM/TB9 is almost 5 times higher than that of TB membrane after 22 relative humidity cycle tests. Moreover, the resulting cell can run smoothly within a wide temperature range from 0 to 160 °C. The single cell performs for over 150 AST cycles and remains stable for >600 h with no visible voltage decay at 80 °C. Therefore, these results indicate the technical feasibility to improve the PA retention via fine-tuning the intrinsic microporosity of the PEMs through a direct blending method.