Structure-Property Based Design of Novel Composite Proton Exchange Membranes

EPSRC：Keenan Smith：EP/L015749/1可持续的能源生产和储存设备对于缓解气候变化对环境和社会的持续影响至关重要。质子交换膜（PEM）是能量存储和转换装置（例如燃料电池（FC）、电解槽和氧化还原液流电池）的重要组件，其在电极之间传导质子，同时最小化反应物分子和电解质阴离子的传输。尽管在这一领域的发展超过了半个世纪，全氟磺酸（PFSA）膜仍然是行业标准。具有互补组件的复合PFSA PEM表现出更高的性能，并缓解了水管理、低温操作和燃料交叉等主要问题，这些问题目前阻碍了这些设备的成功。这个位置集中在我的博士学位的两个主要概念，通过新的制造技术和互补的表征工具，以提供一个完整的结构理解。结晶聚三嗪酰亚胺（PTI），是一种新型的2D材料，正在研究在伦敦大学学院。它表现出3.88个具有突出的哌啶-NH基团的微孔和有利的晶体学堆叠，导致“水通道蛋白样”水运输。我们率先使用超声波喷涂（USP）生产复合聚合物薄膜，在整个PFSA框架中均匀分布PTI和氧化石墨烯（GO）。PTI的特性提供了优于传统聚合物的复合PEM以及GO复合PEM。PTI和GO添加剂在复合PEMS中赋予其有益性能的机制将通过在U.卡尔加里。单层、双层和三层2D材料，如石墨烯和六方氮化硼，被认为是“完美的”燃料电池膜，具有最高的理论质子传导率，这是由于质子选择性渗透通过规则排列的原子晶格的密集电子云。除了前面提到的特定性质之外，这表明PTI具有作为提供不受阻碍的质子传输的薄离子筛分层的显著潜力。然而，在获得大规模的层的PTI的困难限制了使用其显着的通过平面输运性质的应用在FC中。联合Waterloo拥有纳米材料加工方面的专业知识，并利用这一点，使用创新方法以低成本和复杂性开发了密集平铺的2D材料单层薄膜。因此，这些材料被誉为提供FC应用的作用可以通过使用简单的、可缩放的方法将PTI的纳米厚膜集成到PEM中来实现。除了界面分层程序外，Pope教授的小组还建立了一种将离子液体（IL）有效地结合到氧化石墨烯（GO）层中用于电极应用的方法。这种表面活性剂驱动的组装提供了将IL（其可以采用水的质子介体作用）结合到石墨烯薄片的机械坚固框架中的综合途径。这提出了一种具有提供无水和高温质子传导的潜力的系统，克服了目前阻碍PFSA PEM成功的低湿度和高温性能的问题。这里提出的材料和设备的进步，利用2D材料的“奇妙”特性，有可能提供具有更高效率和耐用性的高功率密度FC。结合对这些新材料的结构和机械理解，将绕过商业上可行的系统的障碍，导致新材料渗透到绿色能源市场并超越现有技术。

EPSRC : Keenan Smith : EP/L015749/1Sustainable energy generation and storage devices are critical to mitigate the continued impacts of climate change on the environment and society. Proton exchange membranes (PEM) are vital components of energy storage and conversion devices, such as fuel cells (FC), electrolysers and redox flow batteries, conducting protons between electrodes, whilst minimizing the transport of reactant molecules and electrolytic anions. Despite over half a century of development in this area, perfluorinated sulfonic acid (PFSA) membranes remain the industry standard. Composite PFSA PEMs with complementary components exhibit enhanced performance and alleviate the major issues of water management, low-temperature operation and fuel crossover, currently hindering the success of these devices. This placement focusses on the two main concepts of my PhD, through novel fabrication techniques and complementary characterisation tools to provide a complete structural understanding.Crystalline polytriazine imide (PTI), is a novel 2D material, being studied at UCL. It exhibits 3.88 Å pores with protruding piperidine -NH groups and favourable crystallographic stacking that results in 'aquaporin-like' water transport. We are pioneering the use of ultrasonic spray printing (USP) to produce composite polymer films with homogenously distributed PTI and graphene oxide (GO) throughout the PFSA framework. PTI's properties provide composite PEMs that outperform conventional polymers, as well as GO composite PEMs. The mechanism by which PTI and GO additives impart their beneficial properties, in composite PEMS, will be revealed by fundamental study of water uptake, swelling ratio, phase separation, free volume, and elastic modulus in thin film (<500 nm) samples at U. Calgary. Single-, double- and tri-layer 2D materials, such as graphene and hexagonal boron nitride, have been speculated as 'perfect' fuel cell membranes, with the highest theoretical proton conductivity, due to the selective permeation of protons through the dense electron clouds of regularly arranged atomic lattices. In addition to the specific properties addressed previously, this suggests that PTI has significant potential as a thin ion-sieving layer providing unimpeded proton transport. However, difficulty in obtaining a large-scale layer of PTI restricts the use of its remarkable through-plane transport properties for application in FCs. U. Waterloo has expertise in nanomaterial processing and have used this to develop films of densely tiled 2D material monolayers at low cost and complexity using innovative approaches. Thus, the role these materials were hailed to provide for FC application can be realised by integrating nano-thick films of PTI into PEMs by use of a simple, scaleable approach. In addition to the interfacial layering procedure, Prof. Pope's group have also established a route to effectively incorporate ionic liquids (IL) into graphene oxide (GO) lamellae for electrode applications. This surfactant driven assembly provides a comprehensive route to incorporate IL, which can adopt the proton mediator role of water, into a mechanically robust framework of graphene lamellae. This presents a system that has potential to provide anhydrous and high-temperature proton conduction, overcoming the issues of low-humidity and high-temperature performance that currently hinder the success of PFSA PEMs. The material and device advances, proposed here, that tap into the 'wonder' properties of 2D materials have the potential to provide high power density FCs with greater efficiency and durability. In conjunction with a structural and mechanistic understanding of these novel materials, the barrier to commercially viable systems will be circumvented, resulting in new materials infiltrating the green energy market and surpassing the established technologies.