Preparation of a low proton resistance PBI/PTFE composite membrane

We present a method for fabrication of poly(benzimidazole)/porous poly(tetra fluorocarbon) (PTFE) composite membranes. A coupling agent containing perfluorocarbon sulfonic acid ionomer is used as an interface between PTFE and poly(benzimidazole) (PBI), which contained –NH groups. The porous PTFE substrate was impregnated with a diluted PFSI coupling agent solution. The optimum concentration of the coupling agent solution was that the concentration of coupling agent was just high enough to cover the surface of the fibers of the porous PTFE substrate membranes. The PBI solutions were then fabricated onto the PTFE membranes containing the coupling agent to prepare the proton exchange composite membranes. The PBI/PTFE composite membrane had a film thickness of ∼22 μm and thus a lower proton resistance than a PBI membrane with a film thickness of ∼100 μm. The PEMFC single cell tests showed that PBI/PTFE composite membrane had a better performance than PBI.