基于二氧化钛纳米管阵列的高温有序质子导体及质子传导机理

Proton exchange membrane fuel cell(PEMFC) operated at elevated temperature has the potential to improve the energy density by simplifying the complexity of the system and to make the no-platinum applied possible. One challenge for elevated temperature PEMFC is the membrane that requires reasonable proton conductivity as well as mechanical properties at such operating temperature. Herein, formation of new type of elevated temperature proton condcuting membranes with highly ordered continous proton transportation channel is proposed based on grafting of polymeric ionic liquid proton conductive materials onto highly ordered inorganic matrix surface through in situ free redical polymerization. The proton transporting mechanism is to be investigated by comprehensive study on proton distribution and diffusion using solid state nuclear magnetic resonance, free volume using positron annhilation lifetime, ion distribution using electrostatic force microscopy, microstructure and electrochemical properties as well. Another important content in this proposal is to evaluate the potential application of such membranes in elevated temperature PEMFC system through the investigation of formation and electrochemical properties of membrane electrode assembly and single cells. The innovative point of this study includes the construction of the highly ordered continous proton transportation channel inside the membrane based on the proton transporting mechanism, which further enhances the proton transporting efficiency. The expected results may provide the theroetical guidance and technical support on the design and formation of elevated temperature proton exchange membranes. Moreover, the idea from this project is also applicable to the design of electrolyte with high effecient ion transportatin for lithium ion batteries.

提高质子交换膜燃料电池的工作温度可以有效降低系统的复杂性以提高其能量密度，同时有望实现非铂催化剂的应用。高温运行的燃料电池的主要技术障碍之一则是高温膜材料的开发。本项目从基础研究的角度出发，提出了采用有机-无机复合技术和原位引发自由基聚合技术，通过将咪唑类高温质子导体接枝到有序多孔无机基体膜的孔壁上构建稳定、连续的有序质子传导通道的设计思路。通过固态核磁共振和正电子湮没寿命技术，结合膜的电化学性能和微观结构，研究膜内的高温无水质子传导机制，优化有序有机-无机复合质子交换膜的设计；研究该类复合膜的膜电极和电池制备技术，评估其在不同温度运行的燃料电池中的应用前景。项目的特色在于以高温质子传导机制为基础，构建高温质子交换膜内的连续质子传导通道，提高质子在膜内的传输效率，为具有有序结构的高温质子交换膜的设计提供一定的理论依据。而且，该设计思路也可以为锂离子电池电解质膜的设计提供借鉴。

设计和合成有序离子导体对于提高材料的离子传导能力以及相应的电化学储能器件的性能具有重要的意义。本项目设计了一种基于有机-无机复合的有序离子传导材料，并通过表面引发自由基原位聚合技术将聚合物电解质利用化学键接枝到二氧化钛纳米管阵列内部实现了材料的合成。通过系统研究聚合反应条件对材料的界面性能和离子传导性能的影响，总结了该类有序材料的离子传导机制，即离子在基体-聚合物界面以钟摆的方式实现离子的传导。根据对离子传导机制的认识，我们提出了针对不同应用领域的有序离子传导材料的优化设计和制备方案，并以咪唑类聚离子液体接枝的有序质子导体在高温质子交换膜燃料电池中的应用为例，综合评价了该类材料的应用前景。同时，鉴于本项目所设计的自由基聚合反应的普适性，即几乎所有含有碳碳双键的功能化单体都可以通过该方式进行有序材料的合成，本项目的材料设计和制备理念可以在不同的领域得到应用。