基于碲化镉复合纳米线自组装研究构筑无机有机复合膜电解质

At the present moment, the proton exchange membranes (PEMs) freezing due to the water molecules as proton conduction carriers passing from a liquid to a solid state below freezing point was an important reason to cause the failure on cold start for proton exchange membrane fuel cells (PEMFCs). The development on the anhydrous proton exchange membranes with the low temperature proton conduction was one of the key strategies to solve the problem of cold start for PEMFCs. Ionic liquids as the anhydrous proton conduction carriers have been widely applied to prepare PEMs. Although ionic liquids have attracted researchers' attention, some problems are believed to obstruct their advance in PEMs. For example, the random dispersion of ionic liquids would go against the improvement on proton conduction; ionic liquids swelling polymer skeleton would reduce the tensile stress of membranes. . In this project, the cadmium telluride composite nanowires were prepared to replace ionic liquids as the anhydrous proton conduction carriers in PEMs. First of all, solid cadmium telluride composite nanowires were here synthesized from the interfacial self-assembly of cadmium telluride nanocrystallines with hydrophobic ionic liquids; then the inorganic-organic composite membrane electrolytes were fabricated by the layer-by-layer self-assembly of cadmium telluride composite nanowires with some functioned polymers. The inorganic-organic composite membrane electrolytes were expected to possess a satisfactory proton conductivity value and mechanical strength owing to the ordered distribution of the solid cadmium telluride composite nanowires and the negligible swelling of polymer skeleton. In the interface between cadmium telluride nanocrystalline and hydrophobic ionic liquids, the interaction force between cadmium telluride nanocrystallines and ionic liquids, the “oil-water” interfacial tension and the dipole-dipole interaction among cadmium telluride nanocrystallines constituted the driving force to perform the self-assembly of solid cadmium telluride composite nanowires. For the low temperature proton conduction, the cadmium telluride composite nanowires could be superior to ionic liquid through the systematic investigations on the structure of the cadmium telluride nanocrystalline ligands screening, ionic liquids determination and the reaction condition optimization. Eventually, the chemical and thermal stability, proton conductivity and mechanical property of the cadmium telluride composite nanowires and the fuel cell performance would be test during this project. It was expected that some suitable inorganic-organic composite membrane electrolytes could be screened out as PEMs candidates working under subzero temperature. We hope this project would provide a new idea or choice to solve the problem of PEMs freezing on cold start for PEMFCs under subzero temperature.

质子交换膜在低温下由于作为质子传导载体的水结冰而冻结是导致燃料电池冷启动失败的重要原因。发展可进行低温质子传导的新型非水质子交换膜成为解决燃料电池冷启动失败的策略。在本项目中，以碲化镉纳米晶与离子液体之间的作用力、液液界面张力以及纳米晶之间作用力为驱动力完成碲化镉复合纳米线的界面自组装，碲化镉复合纳米线作为质子传导载体再与聚合物进行层层自组装构筑成无机有机复合膜电解质。虽然碲化镉纳米晶不具备传导质子的能力，但是质子在无机有机复合膜中可借助于碲化镉复合纳米线提供的有序通道进行定向传导，并且固态的碲化镉复合纳米线可避免对聚合物溶胀而且其在复合膜有序分布更有助于质子传导。通过本项目的研究期待在低温条件下（-30℃），构筑的无机有机复合膜电解质的质子电导率达到0.01S/cm，满足燃料电池对质子交换膜的要求，从膜材料角度为解决低温下燃料电池冷启动失败的问题提供新的研究思路以及方法。

近年来，环境污染问题日益突出，因此发展燃料电池汽车作为家用汽车对于解决环境污染问题具有重要的现实意义。目前，实现燃料电池在低温下快速启动是影响燃料电池汽车走进人们生活的技术难题之一。针对质子交换膜中的水结成冰而导致燃料电池无法工作的现实问题，寻找在低温条件下具有良好质子传导能力的质子传导载体代替水分子制备非水质子交换膜电解质具有理论研究以及现实应用的双重价值。本项目提出以碲化镉纳米晶与离子液体自组装为碲化镉复合纳米线，再利用层层自组装法与聚合物构筑无机有机复合膜作为燃料电池的质子交换膜应用于低温非水环境中。.在具体的项目实施过程中，通过界面自组装法制备复合质子传导载体，利用层层自组装技术、旋涂技术、冷冻干燥技术以及真空辅助絮凝技术等构筑具有有序结构的无机有机复合膜并开展复合膜性能的测试研究，明确复合膜有序微观结构与其关键技术性能之间的构效关系，制备的复合膜具有良好的高温以及低温非水条件下的质子电导率，从质子交换膜的方面拓展了质子交换膜燃料电池的应用领域。其中，制备的SPEEK/PVA/PA复合膜在低温下具有良好的质子传导能力以及低温电导率稳定性。在-30oC下，复合膜质子电导率达到3.82×10-2 S/cm，在-30oC且连续测试980 h后，复合膜的质子电导率为3.33×10-2 S/cm。此外，在-30oC至30oC的范围内循环测试7次后，在-30oC下的电导率为5.30×10-2 S/cm，而在30oC下，复合膜的质子电导率达到1.31×10-1 S/cm。制备的复合膜在低温下尤其在冰点下具有良好的质子传导能力，为从膜材料角度解决质子交换膜燃料电池的低温长期存放以及冷启动失败等问题提供了新的研究思路以及策略。