High hydrogen-bond density polymeric ionic liquid composited high temperature proton exchange membrane with exceptional long-term fuel cell performance

Abstract

Achieving the right balance between electrical conductivity and long-term reliability in high-temperature proton exchange membrane (HT-PEM) technologies contributes to sustainable energy recycling. This study involves a groundbreaking effort to create amphiphilic polybenzimidazoles by incorporating 2-isocyanatopyridine into hydroxy-polybenzimidazole (OHPBI). A high hydrogen-bond density network is constructed through two-by-two interactions between the hydroxyl group, the imidazole molecule and quaternary ammonium group. Quaternary ammonium polymeric ionic liquid is introduced to maintain high phosphoric acid (PA) doping and PA retention. The PA retention of the amphiphilic polybenzimidazole membrane is 87.5 % after 240 h at 160 °C/0 % RH. Furthermore, the peak power density of the amphiphilic polybenzimidazole membrane reach 837.8 mW cm⁻² at 180 °C and the voltage decay rate is 0.23 mV h⁻¹ after long-term operation. More specifically, the amphiphilic polybenzimidazole membranes show a conductivity of 138.9 mS cm⁻¹ at 180 °C. This indicates that the amphiphilic polybenzimidazole membrane has both high power output and long-term stability. This work introduces an innovative method to improve the efficiency of PBI-based HT-PEM.