Proton‐Conducting Zirconium Pyrophosphate/Poly(2,5‐benzimidazole) Composite Membranes Prepared by a PPA Direct Casting Method

Zirconium pyrophosphate (ZPP)/poly(2,5‐benzimidazole) composites were prepared by polymerization of 3,4‐diaminobenzoic acid with zirconium hydrogen phosphate in polyphosphoric acid. The composite membranes for polymer electrolyte membranes were prepared by casting the polymerization solutions directly onto stainless steel plates. Membranes doped in 60 wt.‐% phosphoric acid solution had high proton conductivity values of more than 0.12 S · cm−1 (at 180 °C and 1% RH). Physical properties of the doped membranes, including the mechanical strength and dimensional stability, improved as ZPP content in the composites increased to 10–20 wt.‐%. magnified image