Fluorinated Polybenzimidazole/Guanidinium Salt Composite Membranes with Improved Performance for High-Temperature Proton-Exchange Membrane Fuel Cells

Abstract

In this work, fluorine-containing polybenzimidazole (6FPBI) and a benzimidazole-based guanidinium salt (TMG/BIM) were synthesized, and the composite membranes, denoted as 6FPBI-X, were subsequently prepared by incorporating TMG/BIM into the 6FPBI matrix. Compared to the pristine 6FPBI membrane, the incorporation of TMG/BIM significantly enhanced the phosphoric acid (PA) uptake of the composite membranes. Benefiting from the rigid backbone of 6FPBI, the 6FPBI-X membranes maintained excellent chemical, thermal, and dimensional stability. Consequently, these composite membranes exhibited higher PA uptake and proton conductivity than the pure 6FPBI membrane. Specifically, the 6FPBI-3% membrane achieved a PA uptake of 203.7%, a proton conductivity of 0.105 S cm–1, and retained 81.7% of its PA after 120 h. Moreover, a single cell assembled with the 6FPBI-3% membrane demonstrated a high power density of 647.1 mW cm–2 at 160 °C. These results indicate that the 6FPBI-X composite membranes are promising candidates for high-temperature proton-exchange membrane applications.