用于碱性燃料电池的含胍盐接枝共聚物阴离子交换膜的合成和性能研究

A series of novel graft copolymers are synthesized for preparing anion exchange membranes (AEMs) using poly(ether sulfone) as the backbone considering its excellent thermal and chemical stability. Poly(phenyl ether) oligomer is used as the side chain because it has flexible ether bond and multiple active sites, and guanidinium cation is used as the ion conducting group that exhibits outstanding chemical stability. The ion conductivity, mechanical properties, thermal stability, and alkaline stability are measured. The microstructure and morphology of the AEMs are characterized by a variety of techniques. The microstructure of the AEMs is controlled via adjusting the grafting ratio and the length of the side chain of graft copolymer to study the microstructure-property relationship of the membranes. The symbiosis among those influence factors and the dependence of composition-microstructure-property of the AEMs are thus established. The mechanism of micro-phase segregation structure formation is studied under the self-assembly of graft polymer to create a desirable micro-phase segregation structure and construct continuous ion conducting channels inside the membrane. The diffusion of water and hydroxyl ions is measured to study the microstructure of the AEMs and the ion transport mechanism across the membrane using pulsed field gradient nuclear magnetic resonance (PFG-NMR) to elucidate the dominant factor that is responsible for ion conductivity. The degradation mechanism of the AEMs in alkaline media is also studied to improve the chemical stability of the AEMs. This work is believed to provide a guide in the preparation of AEMs with desirable performances.

采用综合性能优异的聚醚砜为主体，含柔性醚键且活性位点较多并可控的聚苯醚低聚物为支链，化学稳定性优异的胍基为离子传输基团，制备新型接枝共聚物阴离子交换膜(AEM)。利用多种技术表征膜的微观结构，并测定膜的机械强度、化学稳定性、电导率等性能。通过调整接枝共聚物的接枝率、支链长度等因素来调控膜的微观结构，探索影响接枝共聚物膜的微观结构及性能的主因，建立膜的组成-微观结构-性能三者之间的内在联系。利用接枝共聚物的自组装行为，研究膜的微相分离结构的形成机制，并创建适宜的微相分离结构，构建连续、高效的离子传输通道，为制备高电导率且燃料渗透性低的AEM提供科学指导。利用脉冲梯度场核磁共振技术测定水分子和OH-离子的扩散系数，研究膜中离子传输机理，揭示影响离子电导率的关键因素。模拟燃料电池工作环境，研究膜在强碱性环境下的降解机理，揭示影响膜的化学稳定性的主因。研究可望为开发高性能的AEM提供科学指导。

阴离子交换膜(AEMs)是燃料电池(FC)的关键部件之一，其性能决定FC的性能和使用寿命。然而，目前研发的AEMs仍然存在离子电导率低和耐碱性差等缺点，严重制约FC的发展。侧链型AEMs能通过自组装形成微相分离，有利于构建高效的离子传输通道，从而提高离子电导率。然而，对于侧链型AEMs的研究尚处于初级阶段，膜结构与性能之间的关系尚未认识清楚，亟待深入探索。.本项目设计了多种侧链型阴离子交换膜，深入研究膜结构与性能之间的关系，主要进展如下：.为同时提高离子电导率和耐碱性能，结合嵌段聚合物能够自组装和侧链结构既能提高离子电导率又能增强稳定性的特点，设计了侧链型三嵌段聚合物阴离子交换膜(ABA-QA-x)。通过调整亲水链段的长度，调控膜的微观结构。透射电镜(TEM)结果显示，膜内存在连续、贯通的离子区域。在80 °C下ABA-QA-3的离子电导率高达105 mS·cm-1，可满足燃料电池对电导率的基本要求。此外，在80 °C、1 M KOH溶液浸泡480 h后，ABA-QA-3仍保留88.9%的离子电导率，耐碱性能尚可。将膜组装成H2-O2型单电池，最高功率密度达176.5 mW·cm-2，可望应用于燃料电池。.基于嵌段结构和侧链结构，增加单条侧链离子基团的数量，通过提高局部离子基团密度的方式获得更高的离子电导率，由此设计了侧链型多季铵功能化AEMs(ABA-TQA-x)。这类膜的最高电导率为130.5 mS·cm-1(80 °C)，高于相同条件下的ABA-QA-x膜。在侧链引入密集的季铵基团，有效抑制了膜的溶胀，使ABA-TQA-x膜具有良好的尺寸稳定性。将ABA-TQA-44膜浸于80 °C、1 M KOH溶液480 h后，电导率和离子交换容量(IEC)仅下降15.3%和16.9%，耐碱性能优。组装单电池最高功率密度达204.6 mW·cm-2，具有实际应用前景。