强耐碱性纯碳氢聚合物电解质膜有序聚集结构的构筑、调控及构效关系研究

Alkaline polymer electrolyte membrane is the key material to enhance the performance/durability of fuel cell and reduce the cost of fuel cell. However, it suffers from two main drawbacks: Low ionic conductivity and poor alkaline stability. Especially, the common alkaline anion exchange membranes based on poly (arylene ether)s undergo chain scission when treated with alkaline condition because of the cleavage of aylene ether bonds on the mainchain backbone. For addressing these problems, this project is proposed to select fully hydrocarbon polymers without the existence of ether bonds as the mainchain backbone, and select the alkyl-tethered quaternary ammonium as the conductive groups of anion exchange membrane in order to enhance the alkaline stability greatly. The self-assembly of hydrophobic and hydrophilic domains of block copolymers would drive the ionic clusters on the pendent side chains to be orderly aggregated, so as to generate bigger ionic clusters and to facilitate the formation of interconnected, broad ionic channels for enhancing the ionic conductivity. By regulating the ionic ordered aggregation structure and the alkaline-resistance backbone, it would result in high conductivity, high dimensional and alkaline stability. The effects of structure parameters, including the mainchain structure, block structure,the length of alkyl side chains and the length of alkyl-tethered ionic side chains on the morphology of membranes will be extensively investigated. It will help us to understand the formation mechanism of organized aggregation structure by self-assembly of block structure and hydrophilic alkyl side chains. It is believed that the systematical study in the relationship of structure-morphology-properties of fully hydrocarbon polymer would provide valuable insights for enhancing the resulted membranes’ properties.

碱性聚合物电解质膜是制约阴离子交换膜燃料电池性能/耐久性提升、成本降低的关键材料，面临着离子传导率低和耐碱稳定性差两大挑战。常见的聚芳醚类碱性聚合物电解质主链中的醚键容易受到OH-的亲核进攻而断裂降解。针对这一关键问题，本项目拟选择不含醚键等不稳定基团的纯碳氢系聚合物作为碱性聚合物电解质的主链骨架，选择与主链长烷基链间隔的季铵阳离子为传导基团，增强所制备膜在高温高碱运行条件下的耐碱稳定性。基于嵌段聚合物清晰的微相分离，促进离子有序聚集结构的形成，构筑连续通畅的离子传输通道，提高离子传输效率。通过离子有序聚集结构和耐碱稳定主链骨架的协同作用，实现高传导率、低溶胀及强耐碱性的目标。拟系统地研究微观相形态结构随主链组成、嵌段结构、疏水烷基侧链和长烷基间隔季铵侧链的链长等结构参数的演变规律，揭示微相有序聚集结构的控制方法。并通过对聚合物结构-相形态-膜性能关系的全面研究，强化阴离子交换膜的性能。

碱性阴离子交换膜燃料电池因氧化还原动力学快、可使用Ni等非贵金属催化剂、成本低等优点，已成为当今燃料电池技术发展和实用化进程中的重要方向。碱性聚合物电解质膜是制约阴离子交换膜燃料电池性能/耐久性提升、成本降低的关键材料，通常面临着离子传导率低和耐碱稳定性差两大挑战。常见的聚芳醚类碱性聚合物电解质主链中的醚键容易受到OH-的亲核进攻而断裂降解。针对这一关键问题，本项目选择聚苯乙烯、聚芳基咔唑和聚芳基哌啶等纯碳氢聚合物作为碱性聚合物电解质膜的主链骨架以避免醚键等不稳定基团和砜基（或羰基）等强吸电子基团的引入，选择与主链长烷基链间隔的季铵阳离子为传导基团以避免苄基位阳离子等不稳定基团的引入，全面增强所制备膜在高温（≥60 ℃）、高碱（pH≥14）运行条件下的耐碱稳定性。通过合理设计聚合物电解质的拓扑结构与交联结构，实现对离子聚集结构的有效调控，促进膜内连续、通畅的离子传输通道的形成，提升碱性阴离子交换膜的传导率。在有效调控离子有序聚集结构和耐碱稳定主链骨架结构的基础上，对上述碱性纯碳氢聚合物电解质膜的相形态结构与宏观性能进行考察，结果表明本项目实现了制备高传导率、低溶胀及强耐碱性阴离子交换膜的目标。将碱性聚合物电解质膜成功组装成膜电极，并成功应用于氢空燃料电池中。本项目的实施，进一步丰富了碱性聚合物电解质的分子结构、微观形貌与综合性能的相互关系，为制备综合性能强化的阴离子交换膜材料提供一定参考和相关科学依据，有利于推动燃料电池的商业化进程。研究成果以论文和专利形式呈现，包括在Journal of Membrane Science、Journal of Materials Chemistry、ACS Applied Materials & Interfaces等本领域国际权威学术期刊上发表论文16篇，授权或申请国家发明专利3件。本项目研究成果作为研究内容的一部分，获得中国石油和化学工业联合会科学技术奖三等奖奖励。