FUEL CELL TECHNOLOGIES FOR AN AMMONIA ECONOMY

我们建议开发一种全新的低温氢燃料电池系统，它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。我们的系统涉及我们自己开发的两项新技术：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，可传导氢氧阴离子，并使用低至零水平的贵金属催化剂），以及基于氨的新型有效的氢气输送方法。我们的氨将来自一个低碳电网平衡项目，该项目由西门子公司领导，由TSB资助，总部设在卢瑟福阿普尔顿实验室。氨能够同时发挥能量缓冲和能量载体的作用（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。建议的氢储存是液态氨，在中等压力（10 - 20个大气压）下储存，在中等温度（350 - 500摄氏度）下使用一种不涉及稀有金属催化剂的新型化学反应机制进行裂解。我们最近发现了一种廉价的氨分解方法，包括通过钠同时进行化学计量分解和酰胺钠的再生：预计其效率损失不到10%。近十年来，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不断提高。一个主要的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被ppm以下的氨不可逆转地损坏。另一方面，碱性燃料电池可以忍受氢燃料中百分之几的氨，而不会造成严重的性能或耐久性损失。碱性聚合物电解质燃料电池甚至以纯氨为燃料运行。这个积极管理的项目（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），以生产性能优于当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双作用碱性离聚体，它可以在催化剂层中导电氢氧阴离子，还可以催化微量氨的分解（以帮助确保燃料电池零氨排放）。阳极催化剂不仅可以在氨的存在下氧化氢，还可以氧化氨本身（同样有助于消除氨的排放），这将是专门针对的。非贵金属阴极催化剂将从目前和以前的研究项目中使用和移植。该项目的高潮将是开发一个综合系统，包括氨裂解装置、结合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。除了测试平台之外，还将进行一项研究，为5kwe系统提供流程和设备设计，以便在未来的项目中与工业界直接合作。

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.