Synthesis and characterization of polybenzimidazole/α-zirconium phosphate composites as proton exchange membrane

To improve the high-temperature performance of proton exchange membranes, the polybenzimidazole (PBI)/α-zirconium phosphate (α-Zr(HPO₄)₂·nH₂O, α-ZrP) proton exchange composite membranes were prepared in this study. PBI polymer containing a large amount of ether units has been synthesized from 3,3′- diaminobenzidine (DAB) and 4,4′-oxybis (benzoic acid) by a direct polycondensation in polyphosphoric acid. The polymer exhibited a good solubility in most polar solvents. Inorganic proton conductor α-ZrP nanoparticles have been obtained using a synthesis route involving separate nucleation and aging steps (SNAS). The effects of α-ZrP doping content on the composite membrane performance were investigated. It was found that the introduction of ZrP improved the thermal stability of the composite membranes. The PBI/ZrP composite membranes exhibited excellent mechanical strength. The composite membrane with 10 wt% ZrP showed the highest proton conductivity of 0.192 S cm^-1 at 160°C under anhydrous condition. The proton conducting mechanism of the PBI/ZrP composite membranes was proposed to explain the proton transport phenomena. The experimental results suggested that the PBI/ZrP composite membranes may be a promising polymer electrolyte used in high temperature proton exchange membrane fuel cells (HT-PEMFCs) under anhydrous condition.