Alkaline Polymer Electrolyte Fuel Cells

第一个可行的大规模燃料电池系统是弗朗西斯·培根开发的液体电解液碱性燃料电池。直到最近，整个航天飞机机队都是由这种燃料电池提供动力的。这些燃料电池的主要困难围绕着液态电解液，液态电解液很难固定，而且由于形成低溶解度的碳酸盐物种而存在问题。随后材料的发展导致了质子交换膜(PEM，例如Nafion(R))的引入和著名的PEMFC的发展。成本是阻碍质子交换膜燃料电池商业化应用的主要因素，主要集中在三个关键部件上：(1)铂催化剂(尽管进行了大量研发，但负载量仍然很高)；(2)质子交换膜；(3)双极板材料(很少有廉价材料可以与超强酸Nafion接触)。由于电渗透阻力，质子交换膜燃料电池内的水平衡很难优化。最后，基于质子交换膜的直接甲醇燃料电池(DMFC)由于甲醇向阴极的迁移(电压损失和燃料浪费)而表现出性能下降。最近材料科学和化学的进步使得膜材料和离聚体的生产成为可能，这将使膜材料和离聚体的开发成为可能。这些碱性阴离子交换膜(AAEM)的应用有望实现燃料电池生存能力的巨大飞跃。申请者团队包括这项创新技术开发的世界领先者。这种燃料电池(传导OH-阴离子而不是质子)提供了许多显著的优点：(1)在碱性条件下，燃料电池反应的催化速度比在酸性条件下更快--事实上，非铂催化剂在这种环境中表现得非常好，例如用于氧还原的银。(2)在碱性环境中比在酸性环境中显示出更多的耐腐蚀性。这增加了可使用的材料的数量和化学成分(包括廉价、易于冲压和薄的金属双极板材料)。(3)非氟离聚体是可行的，有望显著降低膜成本。(4)OH-阴离子导电电解质中的水和离子传输是有利的。电渗透阻力将水从阴极输送出去(防止阴极泛滥，这是PEMFC和DMFC的一个主要问题)。这一过程还缓解了DMFC的“交叉”问题。这项研究计划涉及开发一套实施碱性聚合物电解质膜燃料电池(APEMFC)所需的材料和技术。这项研究将由伦敦帝国理工学院、克兰菲尔德大学、纽卡斯尔大学和萨里大学的世界顶尖材料科学家、化学家和工程师组成的财团进行。该团队代表了进行此类研究的最佳团队之一，在燃料电池系统的所有方面，从基本电催化到电堆水平，包括评估这些系统的诊断方法，体现了对实验和理论水平的多尺度理解。研究小组已经探索了APEMFC的一些方面，该项目将以综合、多管齐下的方法开发新技术的每个方面，同时将正在进行的结果传达给相关行业合作伙伴俱乐部的成员。将充分利用学科跳跃和国际层面合作的广泛机会。总体目标是开发APEMFC的膜材料、催化剂和离聚体，并利用无铂电催化剂建造和运行此类燃料电池。拟议的工作方案是冒险的：然而，除了适当的缓解战略外，还仔细评估了风险(高风险部分承诺高回报，但依赖性很小)。成功将导致英国开创一种新的清洁能源转换技术。

The first viable large scale fuel cell systems were the liquid electrolyte alkaline fuel cells developed by Francis Bacon. Until recently the entire space shuttle fleet was powered by such fuel cells. The main difficulties with these fuel cells surrounded the liquid electrolyte, which was difficult to immobilise and suffers from problems due to the formation of low solubility carbonate species. Subsequent material developments led to the introduction of proton-exchange membranes (PEMs e.g. Nafion(r)) and the development of the well-known PEMFC. Cost is a major inhibitor to commercial uptake of PEMFCs and is localised on 3 critical components: (1) Pt catalysts (loadings still high despite considerable R&D); (2) the PEMs; and (3) bipolar plate materials (there are few inexpensive materials which survive contact with Nafion, a superacid). Water balance within PEMFCs is difficult to optimise due to electro-osmotic drag. Finally, PEM-based direct methanol fuel cells (DMFCs) exhibit reduced performances due to migration of methanol to the cathode (voltage losses and wasted fuel).Recent advances in materials science and chemistry has allowed the production of membrane materials and ionomers which would allow the development of the alkaline-equivalent to PEMs. The application of these alkaline anion-exchange membranes (AAEMs) promises a quantum leap in fuel cell viability. The applicant team contains the world-leaders in the development of this innovative technology. Such fuel cells (conduction of OH- anions rather than protons) offer a number of significant advantages:(1) Catalysis of fuel cell reactions is faster under alkaline conditions than acidic conditions - indeed non-platinum catalysts perform very favourably in this environment e.g. Ag for oxygen reduction.(2) Many more materials show corrosion resistance in alkaline than in acid environments. This increases the number and chemistry of materials which can be used (including cheap, easy stamped and thin metal bipolar plate materials).(3) Non-fluorinated ionomers are feasible and promise significant membrane cost reductions.(4) Water and ionic transport within the OH-anion conducting electrolytes is favourable electroosmotic drag transports water away from the cathode (preventing flooding on the cathode, a major issue with PEMFCs and DMFCs). This process also mitigates the 'crossover' problem in DMFCs.This research programme involves the development of a suite of materials and technology necessary to implement the alkaline polymer electrolyte membrane fuel cells (APEMFC). This research will be performed by a consortium of world leading materials scientists, chemists and engineers, based at Imperial College London, Cranfield University, University of Newcastle and the University of Surrey. This team, which represents one of the best that can be assembled to undertake such research, embodies a multiscale understanding on experimental and theoretical levels of all aspects of fuel cell systems, from fundamental electrocatalysis to the stack level, including diagnostic approaches to assess those systems. The research groups have already explored some aspects of APEMFCs and this project will undertake the development of each aspect of the new technology in an integrated, multi-pronged approach whilst communicating their ongoing results to the members of a club of relevant industrial partners. The extensive opportunities for discipline hopping and international-level collaborations will be fully embraced. The overall aim is to develop membrane materials, catalysts and ionomers for APEMFCs and to construct and operate such fuel cells utilising platinum-free electrocatalysts. The proposed programme of work is adventurous: however, risks have been carefully assessed alongside suitable mitigation strategies (the high risk components promise high returns but have few dependencies). Success will lead to the U.K. pioneering a new class of clean energy conversion technology.