Microphase-separated polybenzimidazole membranes with quaternized polymeric ionic liquid for high-performance and durable HT-PEMs

Synthesis of polymeric ionic liquid HT-PEM with phase separation structure • OHPBI-GPIL-PIM 7.5 has a high PA retention of 89.1%. • The proton conductivity of OHPBI-GPIL-PIM 7.5 membrane is 107.0 mS cm −1 at 180 °C. • OHPBI-GPIL-PIM 7.5 has a peak power density of 1.1 W cm −2 at 180 °C. • The voltage decay rate of the OHPBI-GPIL-PIM 7.5 membrane electrode is 0.05 mV h −1 . Achieving an optimal balance between peak power density and long-term stability in high-temperature proton exchange membrane (HT-PEM) technology is instrumental in facilitating sustainable energy recovery. In this study, we pioneered the design of long alkyl quaternized ionic liquid (GIL) to introduce it into hydroxypolybenzimidazole (OHPBI), to enhance the proton conductivity of OHPBI. Concurrently, we incorporated self-contained microporous polymers (PIM-1) into the system and utilized the differing affinities of GIL and PIM-1 toward the phosphoric acid (PA) phase to prepare microphase-separated polybenzimidazole (OHPBI-GPIL-PIM X ) membranes. Notably, the PA retention rate of the OHPBI-GPIL-PIM X membrane at 160 °C/0% relative humidity is 89.1%. Additionally, the OHPBI-GPIL-PIM X membrane achieves a peak power density of 1.1 W cm −2 at 180 °C, with a voltage decay rate of 0.05 mV h −1 after prolonged operation. The OHPBI-GPIL-PIM X membrane demonstrates both high power output and long-term stability, highlighting its potential for emerging electrochemical applications. Download: Download high-res image (120KB) Download: Download full-size image