Abstract: Poly(2,5-benzimidazole)(ab-PBI) was prepared from 3,4-diaminobenzoic acid via a polymerization reaction.The obtained polymer exhibits an excellent thermal stability at temperatures up to 500 ℃.The membranes of ab-PBI are readily to be doped with phosphoric acid at room temperature.The acid doped ab-PBI membranes present proton conductivity in a level of 10^-2-10^-1 S/cm at temperatures above 100 ℃.The conductivity of the acid doped ab-PBI membranes was studied in a temperature range of 80 to 200 ℃ under different relative humidities and with different acid doping levels.Proton exchange membrance fuel cell(PEMFC) test results indicated that about 200 mW/cm² of power density was obtained with phosphoric acid doped ab-PBI as the electrolyte under atmospheric pressure at 200 ℃ and without humidification.

Key words: Polybenzimidazole; High temperature PEMFC; Proton exchange membrane(PEM); Proton conductivity, Polybenzimidazole, High temperature PEMFC, Proton exchange membrane(PEM), Proton conductivity