FUEL CELL TECHNOLOGIES FOR AN AMMONIA ECONOMY

我们建议为低温氢燃料电池开发一种全新的系统，该系统承诺的性能可以与质子交换膜燃料电池相媲美，但成本更低，更坚固。我们的系统涉及两项我们自己开发的新技术：碱性聚合物电解质燃料电池(包含碱性阴离子交换聚合物电解质材料，传导氢氧化物负离子，并使用低水平或零水平的贵金属催化剂)，以及一种基于氨的新的有效氢气输送方法。我们的氨气将来自一个低碳电网平衡项目，该项目由西门子股份公司领导，由TSB资助，总部设在卢瑟福·阿普尔顿实验室。氨既能发挥能量缓冲的作用，又能起到能量载体的作用(它与丙烷和丁烷等化石燃料碳氢化合物非常相似)，这表明它有可能在未来的低碳经济中发挥核心作用。拟议的氢气储存是液氨，储存在中等压力(10-20大气压)下，在中等温度(350-500摄氏度)下裂解，使用一种不涉及稀有金属催化剂的新型化学反应机制。我们最近发现的廉价氨分解方法包括通过钠同时进行按化学计量的分解和再生：预计这将导致不到10%的效率损失。在过去的十年中，在全固态碱性聚合物电解质燃料电池中使用氢氧化物导电碱性阴离子交换聚合物电解质的研究水平有所提高。这样做的一个主要理由是，这种燃料电池最有希望消除贵金属催化剂。此外，低温(酸性)质子交换膜燃料电池会受到-lt；ppm氨的不可逆转损坏。另一方面，碱性燃料电池可以容忍氢燃料中几%的氨，而不会造成严重的性能或耐用性损失。碱性聚合物电解质燃料电池甚至使用纯氨作为燃料。积极管理的项目(将完全整合到英国的SuperGen氢和燃料电池中心)将涉及开发用于氨分解的新型酰胺和亚胺系统，以及下一代导电和耐用的阴离子交换聚合物电解质和低成本催化剂(与Amalyst Ltd.密切合作)。生产性能优于目前最先进水平的碱性聚合物电解质燃料电池。聚合物电解质的开发将包括新型的双重作用碱性离聚体，它允许氢氧化物负离子在催化剂层中传导，还可以催化痕量氨的分解(以帮助确保燃料电池的氨零排放)。不仅可以在氨存在的情况下氧化氢气，而且可以氧化氨本身(同样有助于消除氨排放)的阳极催化剂将成为特别的目标。非贵金属阴极催化剂将从当前和以前的研究计划中使用和移植。该项目的高潮将是开发一个包含氨裂解装置的联合系统、一个包含已开发技术的碱性聚合物电解质燃料电池、工厂平衡以及控制和监测系统。将系统方法带到试验台之外，将进行一项研究，为5千瓦系统提供流程图和设备设计，并通过与行业直接合作的未来项目推进。

We propose to develop a radically new system for low-temperature hydrogen fuel cells that promises a performance that can match proton-exchange membrane fuel cells but costs less and is more robust. Our system involves two new technologies, which we ourselves have developed: alkaline polymer electrolyte fuel cells (that contain alkaline anion-exchange polymer electrolytes materials that conduct hydroxide anions, and use low to zero levels of precious metal catalysts) coupled with a new effective method of hydrogen delivery based on ammonia. Our ammonia will be sourced from a low-carbon grid-balancing project that is led by Siemens AG, funded by the TSB and based at the Rutherford Appleton Laboratory. The ability of ammonia to fulfil both the role of energy buffer and energy vector (that closely mimics fossil fuel hydrocarbons such as propane and butane) indicates its potential to play a central part in a future low-carbon economy.The proposed hydrogen store is liquid ammonia, stored at modest pressures (10 - 20 atmospheres), which is cracked at moderate temperatures (350 - 500 degC) using a novel chemical reaction mechanism that does not involve rare-metal catalysts. Our recently discovered, inexpensive approach to ammonia decomposition involves the concurrent stoichiometric decomposition and regeneration of sodium amide via sodium: it is anticipated to lead to less than a 10% loss of efficiency.In the past decade, there has been an increased level of research into using hydroxide conducting alkaline anion-exchange polymer electrolytes in all-solid-state alkaline polymer electrolyte fuel cells. A major rationale for this is such fuel cells hold the most promise for the elimination of precious metal catalysts. Additionally, low temperature (acidic) proton-exchange membrane fuel cells are irreversibly damaged by < ppm amounts of ammonia. Alkaline fuel cells, on the other hand, can tolerate several % of ammonia in the hydrogen fuel without serious performances or durability losses. Alkaline polymer electrolyte fuel cells have even been operated with pure ammonia as the fuel.The actively managed project (that will fully integrate into the UK's SuperGen Hydrogen and Fuel Cell Hub) will involve the development of novel amide and imide based systems for ammonia decomposition as well as the next generation of conductive and durable anion-exchange polymer electrolytes and low cost catalysts (in close partnership with Amalyst Ltd.) to produce alkaline polymer electrolyte fuel cells with improved performances over the current state-of-art. The polymer electrolyte development will include novel dual role alkaline ionomers that allows conduction of the hydroxide anions in the catalyst layers and also catalyses the decomposition of trace ammonia (to help ensure zero ammonia emissions from the fuel cell). Anode catalysts that can not only oxidise hydrogen in the presence of ammonia, but oxidise the ammonia itself (again to help eliminate ammonia emissions) will be specifically targeted. Non-precious-metal cathode catalysts will be used and ported from current and prior research programmes.The culmination of the project will be the development of a combined system incorporating the ammonia cracker, an alkaline polymer electrolyte fuel cell incorporating developed technologies, balance-of-plant, and a control and monitoring system. Taking the systems approach beyond the test bed, a study will be performed that delivers flowsheet and device designs for a 5 kWe system to be taken forward via future projects in direct collaboration with industry.