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)是燃料电池(FC)、电解器和氧化还原液流电池等能量存储和转换设备的重要组成部分，它在电极之间传导质子，同时最大限度地减少反应物分子和电解性阴离子的传输。尽管在这一领域已经发展了半个多世纪，但全氟磺酸(PFSA)膜仍然是行业标准。具有互补成分的复合全氟辛烷磺酸质子交换膜表现出更高的性能，并缓解了目前阻碍这些装置成功的水管理、低温操作和燃料交叉等主要问题。本文重点介绍了我博士学位论文的两个主要概念，通过新颖的制造技术和互补的表征工具来提供完整的结构理解。晶体多三氮杂酰亚胺(PTI)是一种新型的2D材料，正在UCL进行研究。它显示出3.88？孔，带有突出的哌啶-NH基团和良好的晶体堆积，导致了类似水通道的水传输。我们率先使用超声波喷印(USP)来生产在整个PFSA框架中均匀分布的PTI和氧化石墨烯(GO)的复合聚合物薄膜。PTI的特性提供了性能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中的有益性能的机理将通过对薄膜(&lt；500 nm)样品的吸水率、溶胀率、相分离、自由体积和弹性模量的基础研究来揭示。单层、双层和三层2D材料，如石墨烯和六方氮化硼，由于质子选择性地透过规则排列的密集电子云，被认为是具有最高理论质子导电性的完美燃料电池膜。除了前面提到的特殊性质外，这表明PTI作为一种薄的离子筛层具有巨大的潜力，可以提供畅通的质子传输。然而，获得大规模PTI层的困难限制了其显著的透面传输特性在FCS中的应用。U·滑铁卢在纳米材料加工方面拥有专业知识，并利用这一技术利用创新方法以低成本和复杂性开发出致密铺设的2D材料单分子层薄膜。因此，这些材料为FC应用提供的作用可以通过使用简单、可扩展的方法将PTI的纳米厚膜集成到PEMS中来实现。除了界面分层过程外，Pope教授的团队还建立了一种将离子液体(IL)有效地结合到氧化石墨烯(GO)薄片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一条全面的途径，将可以采用水的质子介体作用的IL整合到石墨烯片层的机械坚固框架中。这提供了一种有潜力提供无水和高温质子传导的系统，克服了目前阻碍全氟辛烷磺酸质子交换膜成功的低湿度和高温性能问题。这里提出的材料和设备的进步，利用2D材料的“神奇”特性，有可能提供更高效率和耐用性的高功率密度FCS。结合对这些新材料的结构和机械方面的了解，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过现有技术。

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.