Ionic Liquid Composite Polybenzimidazol Membranes for High Temperature PEMFC Applications.

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Polybenzimidazole (PBI) membranes are crucial for high-temperature fuel cells but often require conductivity enhancement.
• Ionic liquids (ILs) offer potential as conductive fillers due to their unique properties.

Purpose of the Study:

• To develop novel polybenzimidazole (PBI) composite membranes with enhanced proton conductivity.
• To investigate the influence of ionic liquids (ILs) with varying anions on PBI membrane performance.
• To evaluate the thermal, mechanical, and electrochemical properties of the developed composite membranes.

Main Methods:

• Preparation of PBI composite membranes using a casting method with 5 wt.% ILs.
• Systematic investigation of proton conductivity using electrochemical impedance spectroscopy.
• Analysis of the effects of different anions and temperature on conductivity.

Main Results:

• The composite membranes demonstrated good thermal, dimensional, mechanical, and oxidative stability.
• PBI membranes incorporating 1-butyl-3-methylimidazolium (BMIM)-derived ILs showed significantly enhanced proton conductivity.
• A peak conductivity of 0.098 S·cm⁻¹ was achieved at 120 °C for membranes containing BMIM with a tetrafluoroborate anion.

Conclusions:

• Ionic liquids, particularly BMIM-tetrafluoroborate, effectively enhance the proton conductivity of PBI membranes.
• The enhanced conductivity is likely due to hydrogen-bond networks formed between ILs and phosphoric acid.
• These PBI-IL composite membranes show promise for high-temperature fuel cell applications.