Mechanically strong sulfonated polybenzimidazole PEMs with enhanced proton conductivity

Proton exchange membranes (PEMs) with good proton conductivity and mechanical properties are highly desired for applications in fuel cells. This work immobilized sulfonic acid groups stably into polybenzimidazole (PBI) by a solid phase reaction. The structures of the sulfonated PBI (s-PBI) are characterized by FT-IR spectroscopy. The proton conductivity and mechanical properties of s-PBI are measured. The s-PBI PEMs showed improved proton conductivity as increasing the amount of azides when comparing to the pure PBI PEM. The strength and modulus of s-PBI PEMs are decreased, but still much larger than s-PBI PEMs prepared by acid doping, sulfonation, and blending. Such s-PBI PEMs made by solid phase reaction would be good candidate for fuel cell applications.