Studies on proton conductivity of polyimide/H 3PO 4/imidazole blends

Abstract

A new anhydrous proton conducting material based on polyimide(PI)/H 3PO 4/imidazole(Imi) Blends was prepared. FTIR spectrum shows the existence of hydrogen bonds between protonated and unprotonated imidazole units. The addition of phosphoric acid can accelerate the degradation process of PIs, while the addition of imidazole in PI/H 3PO 4 blends can improve their chemical oxidation stability enormously. The proton conductivity of PI/H 3PO 4 blends increases significantly with increasing content of imidazole. Proton conductivity of PI/ xH 3PO 4/ yImi membranes increases with increasing temperature and content of phosphoric acid. The experimental results show that it is possible to significantly improve the operating temperature of PEM fuel cell system by replacing water with imidazole as proton solvent in the polymer membrane. Hydrogen bond seems to play an important role in the proton conductivity of this system. The decrease of proton conductivity of imidazolium phosphate shows in some degree that the interaction between imidazole and phosphoric acid is not the main reason for the conductivity increment of imidazole doped PI/H 3PO 4 system.