磺化聚酰亚胺-磷酸锆高温质子交换复合膜结构设计与质子传导性能研究

Proton exchange membrane (PEM) is one of the key components for the fuel cells system. Perfluorosulfonic acid(PFSA) membranes are the most used as PEM in business application. However further progress in this field has been restricted as their high cost, dramatic decreasing in the proton conductivity of PFSA membrane at high temperature. Hence, there is an urgent need for fuel cells to explore new proton exchange membranes that can achieve high performance at low cost and high temperature. This project was planned to design and screening good proton conductivity of sulfonated polyimide structure with molecular simulation Materials Studio software calculation, thus decreased the blindness in membrane preparation. Zirconium phosphate used as inorganic proton conductors were inserted into sulfonated polyimide which have high thermal stability. The novel sulfonated polyimide-zirconium phosphate proton exchange composite membranes were prepared by Sol-Gel method. The problem of zirconium phosphate dispersibility can be solved. The effect of microstructure on the thermal stability, water retention and proton conductivity of proton exchange membrane were investigated by exploring the relationship between the microstructure and properties for different proton exchange composite membrane. The mechanism of membrane proton conductivity and water retention were clarified. A series of proton exchange composite membranes with high proton conductivity, low cost, good thermal stability were expected to be prepared.

质子交换膜是燃料电池的核心材料，全氟磺酸膜是商业应用最多的质子交换膜，但其成本过高，高温下膜的质子传导性能急剧下降等缺点限制了全氟磺酸膜的商业化应用。因此，开发低成本、耐高温的新型质子交换膜成为燃料电池技术亟待解决的关键问题。本项目拟从分子设计角度出发，采用分子模拟Materials Studio软件设计筛选具有良好质子传导能力的磺化聚酰亚胺结构，减少实验的盲目性。通过无机质子导体磷酸锆的引入，使其固定在热稳定性好的磺化聚酰亚胺高分子主链上，通过溶胶-凝胶法制备新型磺化聚酰亚胺-磷酸锆质子交换复合膜，解决磷酸锆在复合膜中的均匀分散性问题，深入探究不同的质子交换复合膜的微观结构与性能之间的关系，得出膜的微观结构对膜的稳定性，保水性能和质子传导性能的影响，阐明高温下质子交换复合膜的质子传导机理和保水机理，以期制备出一系列在高温下具有高质子电导率、低成本、良好热稳定性的新型质子交换复合膜。

本项目旨在开发高效低成本的非氟质子交换膜材料，通过分子动力学模拟方法对不同结构的直链和侧链型SPI进行质子传导性能模拟，将模拟数据与实验数据比对，验证模拟方法的正确性，筛选出性能最优的含有侧链型磺化二胺单体结构的SPI(NTDA-2,2’-BSPB/BAPB 2:1）。. 通过无机质子导体α-ZrP的引入，成功开发了ZrP掺杂的侧链型SPI质子交换复合膜。ZrP增强了复合膜的热稳定性，无机支撑结构形成于膜内增强了膜的机械性能和抗溶胀性，但限制了膜充分吸水。ZrP连接SPI侧链磺酸簇形成质子传输网络通道，通过自由体积的抑制，增加膜内有效质子传输体积。当温度升高到90 °C时，复合膜的质子电导率均高于SPI膜，SPI/ZrP-20膜的质子电导率达到0.186 S•cm-1。. 为了改善复合膜的含水状况，选用具有良好储水空间和亲水性的ZrPSPP，成功研制了SPI/ZrPSPP质子交换复合膜。ZrPSPP提高了膜的热稳定性，支撑结构的形成抑制膜的溶胀，增加了膜的含水率。ZrPSPP增加了膜的IEC值，其磺酸基团可作为质子供体和扩散的载体增强质子的跳跃，膜内水的增加同时增强运载和跳跃。复合膜的质子电导率随ZrPSPP含量的增加而增加，SPI/ZrPSPP-20的复合膜在90 °C去离子水的质子电导率达到0.191 S•cm-1超过Nafion 117膜。探讨ZrP及其衍生物对复合膜质子传输和保水性能的影响，揭示了复合膜的质子传导机理，质子传递过程主要发生在粒子层间和表面的酸基团与水、酸与酸之间，产生的水合氢离子与附近磺酸亲水团簇形成氢键网络并促进质子传递。. 为了提高质子交换膜在高温和低湿度条件下的热稳定性、机械性能和质子传导性能，开发了PBI/ZrP质子交换复合膜。复合膜的热稳定性随ZrP含量的增加而增加可达到550℃。复合膜表现出较高的拉伸强度和断裂伸长率，保证了电池能够稳定运行。在无外界加湿的条件下，PBI/ZrP-10%复合膜的质子电导率在160℃达到0.192 S•cm-1，利用Grotthuss机制解释了高温下PBI/ZrP 复合膜中的酸碱质子传导机理。通过本项目的实施开发了三种新型非氟质子交换复合膜材料，拓展了膜材料的种类。为今后研究高温下性能优良，低成本的质子交换膜打下了坚实的基础，提供了理论和实验的依据。