基于纳米碳管类流体—壳聚糖自组装的质子交换膜

In order to overcome the chitosan (CS) used as proton exchange membrane (PEM) with the defects of low proton conductivity, low flexibility and low mechanical properties. In this project, a novel method is developed to prepare self-assembly PEM with CS and solvent-free carbon nanotubes fluids. First, carbon nanotubes (CNTs) surface will be modified by long chain organic ion salt to prepare solvent-free carbon nanotubes fluids. Then, the excellent performance PEM is prepared by self-assembly with CS and solvent-free carbon nanotubes fluids in dilute solution. The -SO3- group introduced by grafting organic molecule chain onto solvent-free carbon nanotubes fluids surface can enhance ionic conductivity of the membrane. Meanwhile, the grafted organic coating can effectively reduce the change of electron transportation in the membrane. The special mobility of solvent-free carbon nanotubes fluids can promote the dispersion of CNTs in the membrane. The reinforcement and plasticization of CNTs can be given full pay to. The relationship between rheological behavior of solvent-free carbon nanotubes fluids and the length of CNTs, composition and structure of organic ion salt will be systematically studied. Moreover, the relationship between proton conductivity, methanol barrier property, mechanical properties, thermal properties of the membrane and morphology, doping ratio of solvent-free carbon nanotubes fluids will be systematically studied as well. The formation mechanism of the self-assembly structure of the membrane is also revealed. At last, the novel method and theoretical foundation is provided to obtain high performance organic-inorganic composite PEM.

为克服壳聚糖（CS）作为质子交换膜使用存在的质子传导率低，膜柔韧性和机械性能不足的缺陷。本项目拟设计一种结构新颖的壳聚糖/纳米碳管类流体自组装复合质子交换膜。首先用具有长链的有机离子盐对纳米碳管（CNTs）进行表面修饰制备纳米碳管类流体，然后在稀溶液中将其与CS组装制备性能优异的复合质子交换膜。纳米碳管类流体表面接枝有机分子长链上引入的-SO3-基团可提高复合膜的离子电导率，同时有机层能有效屏蔽CNTs在复合膜中可能形成的电子短路。纳米碳管类流体特殊的流动性促进了CNTs在CS基体中的分散，充分发挥了其增强增塑作用。本项目系统研究了纳米碳管类流体的流变特性与CNTs长度、有机离子盐组成和结构的关系，进一步研究了复合膜的质子传导率、阻醇性能、力学性能、热学性能与纳米碳管类流体形态、掺杂比例之间的关系，揭示复合膜组装结构的形成机制，为高性能有机-无机复合质子交换膜的研究提供新的方法和理论基础。

质子交换膜是质子交换膜燃料电池和直接甲醇燃料电池的关键部件，壳聚糖（CS）作为一种最有研究潜力的质子交换膜，具有价格低廉、环境友好性，可用于高温和低湿度环境，低的甲醇渗透率，同时分子结构上富含-OH和-NH2，可通过对其进行分子设计实现可控化学修饰，但CS作为质子交换膜使用存在质子传导能力低，膜的柔韧性、机械性能和热稳定性不足的问题。为了克服CS作为质子交换膜使用存在的上述缺陷，本项目提出了采用表面改性的碳纳米管（CNTs）对CS进行多功能化改性的思路，有三个主要研究内容：CNTs类流体对质子交换膜的多功能化改性研究；无机氧化物包覆CNTs对质子交换膜的多功能化改性研究；有机高分子包覆CNTs对质子交换膜的多功能化改性研究。研究结果表明：类流体技术及表面改性能明显促进CNTs在复合膜中的分散与界面粘接，实现其对复合质子交换膜的增强、增韧和阻隔甲醇的效果；同时，表面包覆层达到一定厚度时，能有效屏蔽CNTs 在复合膜中可能形成的电子短路，进一步增加复合膜的导质子能力。本项目的实施对加快燃料电池的商业化进程具有十分重要的应用价值，同时，通过探讨改性碳纳米管对复合质子交换膜的增强增韧、质子传导和阻醇机理，具有重要的科学意义和理论价值。