Quaternary Ammonium Groups Modified Cross-linked Polybenzimidazole for Catalyst Slurry and Proton Exchange Membranes in Fuel Cell
摘要
We successfully incorporated phenyl groups into a small-molecule quaternary ammonium cross-linker and synthesized cross-linked polybenzimidazole membranes via a one-step cross-linking process. Compared with conventional quaternary ammonium-crosslinked benzimidazole membranes, the introduction of phenyl groups significantly increases the free volume within the membrane. After phosphoric acid doping, the benzimidazole membrane with larger free volume retains more phosphoric acid compared to conventional quaternary ammonium-crosslinked membranes, forming an extensive hydrogen-bonding network that effectively enhances its anhydrous proton conductivity. The anhydrous proton conductivity reaches 91 mS·cm−1 at 160 °C, substantially higher than that of conventional quaternary ammonium-crosslinked membranes with the same mass fraction. Benefiting from the improved conductivity, the membrane electrode assembly exhibits reduced ohmic polarization, achieving a peak power density of 792 mW·cm−2 at 160 °C.