Abstract:  Molecular weight is one of the essential parameters which can characterize the polymer features. It plays an important role in the performances of membrane electrode assembly (MEA). Poly(2,5-benzimidazole) (ABPBI) is the simplest type of the benzimidazole polymer. It can be prepared easily by a single monomer, and the —N groups combining with acid by the hydrogen bond. It possesses high proton conductivity. In this work, different molecular weight ABPBIs were synthesized, and the ABPBIs were used to fabricate MEAs. The performances of the MEAs were studied by polarization curves and electrochemical impedance spectroscopy (EIS). The results showed when ABPBI was the least molecular weight, MEA had the best performance. Moreover, the resistances of MEA were decreased as the current density was increased.

Key words: poly(2,5-benzimidazole), molecular weight, high temperature proton exchange membrane fuel cell, membrane electrode assembly, electrochemical impedance spectroscopy

摘要： 聚合物分子量是表征聚合物特征的基本参数之一，分子量不同,聚合物的性能差异很大，其对高温质子交换膜燃料电池膜电极的输出性能亦起着至关重要的作用。聚（2,5-苯并咪唑）(ABPBI)的结构简单, 合成方便，可由单一单体聚合而成， 而且其每一个苯并咪唑重复单元上的-N 基团都可与酸以氢键的方式结合, 因而呈现较好的质子电导率。合成了4种不同分子量的ABPBI，采用自制ABPBI膜作为电解质，Pt/C为催化剂，研究了不同分子量ABPBI配制的浆料组装的氢氧高温燃料电池的性能，通过极化曲线测试可以看出聚合物分子量越小膜电极(MEA)性能越好。进一步对膜电极交流阻抗性质进行了研究，经Zsimpwin软件拟合得出，分子量越大电荷转移电阻越大，与极化曲线测试结果相符，并且随着电流密度的增大，各部分电阻均成下降趋势。

关键词: 聚（2,5-苯并咪唑）, 分子量, 高温质子交换膜燃料电池, 膜电极, 交流阻抗