沿离子传导方向具有直通有序离子传导通道的电纺氢氧离子交换膜

Hydroxide exchange membrane (HEM) is the key of renewable power sources, such as fuel cell and redox flow battery. It has many advantages, such as coordinating with non-noble metals, low methanol and vanadium ion crossover. The inherently low mobility of hydroxide ion conduction makes the design of efficient hydroxide ion conductive channels becomes particularly important for HEMs to improve conductivity. However, poor connection between ionic conductive pathways is a serious problem for HEMs to improve hydroxide conductivity. In this project, a novel design of straight aligned ionic conductive channels is proposed, which is accordance with the hydroxide conducting derection in the practical fuel cell operation. Aligned nanofiber will be produced by electrospinning and then be erected along the through-plane (membrane thickness) direction of the membranes by the post pore-filling of membrane. Straight ionic conductive pathways are expected to be built along the surface of the electrospun nanofiber to improve the hydroxide conductivity in the through-plane direction of the membranes. The aligned morphology control and the pore-filling process will be investigated in order to preparae aligned fiber membranes with high performance. We propose surface self-assembly mechanism of the ionic clusters induced by high-voltage electric field. It will be investigated systematically. Transport of hydroxide ions across the membranes and the catalyst layers will be balanced by controlling the membrane fabrication. Optimized relationship between the structural parameters of the membranes and the properties, such as conductivity and alkaline stability of the cells will be established to achieve high utilization efficiency of the ionic conducting groups. There is no report in the literature of the through-plane aligned electrospinning hydroxide exchange membrane and the surface ionic cluster transport mechanism, to our best knowledge. The achievements of this project will be helpful to improve the efficiency and economy of the renewable power resources, such as fuel cell.

氢氧离子交换膜是决定新能源燃料电池、液流电池性能的核心部件，可配合非贵金属催化剂，甲醇、钒离子等渗透率低。但氢氧根离子活动性差的本质，要求膜具有高度连通的离子传导通道。针对因离子传导通道连通性差导致膜电性能低的关键问题，本文提出沿离子传导方向具有直通有序离子传导通道的电纺氢氧离子交换膜。按照电池要求，将电纺纳米荷电纤维沿离子传导(膜厚度)方向直通有序排列，荷电纤维表面形成离子传导通道。研究电纺纳米纤维的直通取向形貌控制及其与堵孔制膜匹配原则，揭示强电场引力使荷电基团向纤维表面迁移的表面离子传导机理，匹配电纺膜与催化层的离子传导速率，建立膜结构与碱性稳定性及电池性能的优化设计，制备高电性能氢氧离子交换膜。项目提出沿离子传导方向直通有序离子传导通道的电纺氢氧离子交换膜及其独特的表面离子传导机理，国内外未见报道，我国将拥有完全自主知识产权。研究成果将作为燃料电池的核心部件，实现高效、低成本运行。

新能源及其高效利用是我国的重大需求。氢氧离子交换膜是燃料电池的核心部件，可配合非贵金属催化剂，甲醇、钒离子等渗透率低。但氢氧根离子解离程度低、非氟芳杂环膜材料主链刚性强的本质，导致膜中离子传导通道连通性差、电性能难以提高。.本文提出沿离子传导方向具有直通有序通道的电纺氢氧离子交换膜。按照电池要求，将电纺纳米荷电纤维沿离子传导(膜厚度)方向直通有序排列，荷电纤维表面形成离子传导通道。提出电纺有序纤维、层叠、堵孔、切片、热压平整化的沿离子传导方向直通有序电纺膜制备工艺；提出同质堵孔、热压堵孔等纤维与堵孔方法匹配提高膜相容性的方法；设计同轴电纺核-壳纤维膜，限域功能化石墨烯、碳纳米管沿纤维取向及强迫相容，协同增强离子传导率和机械强度。电纺膜获得高氢氧根离子传导率和低溶胀度（30℃离子传导率67.5 mS/cm，60℃溶胀22.5%）。依据离子簇TEM和SAXS，提出电纺纤维的表面离子传导方式，设计多种荷正电功能基团主/侧链结构调控有序离子通道形貌，揭示强电场引力使荷电基团向纤维表面迁移、提高离子传导率的作用机制。建立膜结构与碱性稳定性间实验关联，揭示电纺膜长程有序微相分离结构有效阻隔氢氧根进攻的独特碱稳定性控制机制，分子设计碱稳定功能基团和主链结构。电纺膜热碱稳定性显著提高（1 M 60oC NaOH中浸泡196h后离子传导率保持85.8%，浇铸膜仅为20%）；研究电纺膜与催化层的离子传导速率匹配，开发热压平整工艺降低膜与催化层接触电阻；建立膜结构与单电池性能间的构效关系，制备高电性能氢氧离子交换膜。电纺荷正电膜氢氧燃料电池功率密度达到浇铸膜电池的2.4倍，电纺荷负电膜甲醇燃料电池功率密度达到Nafion115膜电池的1.5倍，实现其高效、低成本运行。发表SCI/EI收录学术论文38篇，会议论文34篇，博/硕士论文2/26篇，开展国际交流26人次，授权/申请中国发明专利5/11项。