碱性燃料电池用“侧链型”梳状阴离子交换膜的制备与性能研究

To produce an anion-conductive and durable anion exchange membrane (AEM) for alkaline fuel cell applications, a series of comb-shaped model compounds and poly(2,6-dimethyl phenylene oxide)s (PPO) with pendant clicked 1,2,3-triazole and quaternary ammonium groups will be synthesized by through CuI-catalyzed "click chemistry" which is a well-known method for linking reaction partners with high efficiency under moderate reaction conditions, and is largely solvent insensitive. The pendant architecture and alkyl side chain are expected to improve the alkaline stability of AEMs, even at high temperature and concentration of base solution because of the steric hinder effect of large volumn alkyl chain which will protect the quaternary ammonium groups from attacking by hydroxide. The degradation mechanism of model compounds will be investigated in detail by quantitative NMR technique which will help us to design and prepare highly base stable AEMs. Moreover, the comb-shaped polymeric architecture having one alkyl side chain and clicked 1,2,3-triazoles which are expected to form a dense, continuous 3D network of hydrogen bonds with hydroxide and water are believed to improve the hydroxide transport in AEMs significantly. In addition, due to the high reactivity of "click chemistry", a variety of functional groups which could improve the properties of AEMs, such as hydroxide transport facilitators PEG, crosslinking technique could be introduced into AEMs quantitatively. Thus, high performance AEMs probably could be obtained by molecular level design. Finally, the MEAs based on above AEMs or ionomers will be prepared for alkaline hydrogen/oxygen fuel cells testing. The durability of fuel cells will be measured. And, the miscibility between ionomers and catalyst nanoparticles, and the effect of polymer architecture on the fuel cell performance will be studied. We believe that the proposed investigations will give us the insight and directions for anion exchange membrane design and preparation.

针对阴离子交换膜普遍存在的碱稳定性差、离子传导率低及膜电极电池性能差等问题，研究"侧链型"梳状季胺化的聚苯醚分子链结构与膜性能的关系。采用高效"点击化学"合成方法，一步制备同时具有"侧链型"分子链结构、三唑及季胺基团、长脂肪链的模型化合物或聚苯醚共聚物。"点击化学"具有非常高的反应活性和选择性，因此可以在聚苯醚中定量的引入具有不同分子链结构的季胺基团、其他功能优化基团，例如交联剂、亲水基团等。通过研究模型化合物稳定性获得季胺基团降解机理。通过研究膜电极组装和电池性能，获得分子链结构、功能基团种类与含量对聚合物与催化剂相容性的影响规律，从而获得对电池性能的影响。因此，本项目的研究不仅为阴离子交换膜的制备提供了新的、方便有效的方法及路线，并有望获得多种具有自主知识产权的阴离子交换膜材料。

本项目以构建高效离子传输、高稳定性的梳状阴离子交换膜为导向，通过高效的“点击化学”反应，1）发展新型侧链型、梳状、大位阻阳离子基团阴离子交换膜材料的制备方法，形成有利于离子传输的纳米通道，解决阴离子交换膜电导率较低的关键科学问题；2）通过分子结构设计和对比研究，明晰阴离子交换膜材料分子链结构与性能之间的关系，为设计高电导率、高稳定性阴离子交换膜材料提供理论依据，并在季铵化聚合物中定量引入优化功能基团，得到高性能的交联型和接枝型阴离子交换膜材料，其中新型接枝阴离子交换膜具有优异的综合性能（IEC为1.69 meq./g时，室温氢氧根电导率达到50.9 mS/cm）；3）初步研究膜与催化剂层的界面相容性对电池性能的作用机制，发现膜在碱性燃料电池中新的降解机制，并提出器件稳定性不能单纯通过膜的碱稳定性测试来表征。基于上述工作，本项目已经在Energy Environ. Sci.，J. Mater. Chem. A（3篇）、J. Membr. Sci. (6篇)等主流期刊发表论文14篇，并受邀在《科学通报》燃料电池阴离子交换聚合物膜专刊撰写研究进展一篇，受到国内外同行的广泛关注。