Improved hydrogen-steam electrodes for solid oxide electrolysers

氢正日益成为一种有吸引力的低碳能源载体，以支持工业热力、化学品、重型车辆、航运和火车等难以解决的行业的脱碳。沿着欧洲氢能战略的推出，2020年11月英国政府绿色计划中大规模纳入氢能，以及最近推出的英国氢能战略，这一点在全球范围内得到越来越多的认可。这些战略的重点是在可再生电力的驱动下，利用电解生产“绿色”氢气。如今，全球96%的氢气来自化石燃料，全球6%的天然气和2%的煤炭消费用于制氢，主要用于石化产品。目前，绿色氢是最昂贵的氢形式，大约60-80%的成本来自电力输入的成本。影响这一点的关键因素是电解槽本身的效率。电解槽分为两类：低温（70- 120 ℃）和高温（600- 850 ℃）。虽然基于碱性或聚合物技术的低温电解槽系统已经成熟并可商购，但其相对适中的效率（约65%）意味着固体氧化物电解槽（SOEC）在更高的温度（600- 900 ℃）下操作，其中水分解的热力学和动力学都更有利，受到越来越多的关注。事实上，由可再生电力驱动的高温蒸汽电解是生产氢气的最有效方式，蒸汽电解到氢气的电效率超过90%，并且有可能将废热整合到吸热过程中以进一步降低电能需求。然而，使用固体氧化物电解池（SOEC）的高温电解还不是一种成熟的技术，只有一家公司（Sunfire）在任何规模上进行测试。许多公司现在正在参与开发SOEC电池堆和系统的竞争，例如美国的燃料电池能源和Bloom，以及英国的Ceres Power。然而，SOEC系统的主要缺点之一是它们的寿命显著低于聚合物电解质和碱性电极竞争者。镍的降解-在氢/蒸汽侧广泛使用的电极材料，在电解槽中发现的高蒸汽含量中是严重的，并且是整个电池降解的主要来源。虽然Ni是传统SOEC燃料电极中的重要组分，其中它既充当催化剂又充当电子导体，但找到具有更好的热稳定性和氧化还原稳定性的替代物来取代镍的作用将是有益的。特别关注利用结合到常规复合材料中的镍溶出的二氧化铈和我们的新型电纺材料来产生用于固体氧化物电解槽的高性能和耐用的氢-蒸汽电极，这将有助于加速其正在进行的开发和部署，从而降低绿色氢气生产的成本。

Hydrogen is increasingly emerging as an attractive low carbon energy carrier to support the de-carbonisation of hard to address sectors such as industrial heat, chemicals, heavy duty vehicles, shipping, and trains. This is being increasingly recognised globally, along with the launch of a European hydrogen strategy, the inclusion of hydrogen at scale in the November 2020 UK Government Green plan, and the recent launch of the UK Hydrogen strategy. Much of the focus of these strategies is on the production of 'green' hydrogen using electrolysis, driven by renewable electricity. Today, 96% of hydrogen globally is produced from unabated fossil fuels, with 6% of global natural gas and 2% of coal consumption going to hydrogen production, primarily for petrochemicals. Currently green hydrogen is the most expensive form of hydrogen, with around 60-80% of the cost coming from the cost of the electrical power input. A critical factor that influences this is the efficiency of the electrolyser itself. Electrolysers fall into one of two categories: low-temperature (70-120C) and high temperature (600-850C). While low temperature electrolyser systems based around alkaline or polymer technology are already mature and commercially available, their relatively modest efficiency (around 65%) means that the solid oxide electrolyser (SOEC), which operates at much higher temperatures (600-900C) where both the thermodynamics and kinetics of water splitting are more favourable, is of growing interest. Indeed, high temperature steam electrolysis driven by renewable electricity is the most efficient way to produce hydrogen, with electrical efficiencies for steam electrolysis to hydrogen of over 90%, and with the possibility of integrating waste heat into the endothermic process to further reduce the electrical energy requirements.However, high temperature electrolysis using solid-oxide electrolyser cells (SOECs) is not yet a mature technology, with only one company (Sunfire) testing at any scale. A number of companies are now entering the race to develop SOEC stacks and systems, such as Fuel Cell Energy and Bloom in the USA, and Ceres Power in the UK. However, one of the major drawbacks of SOEC systems is that their lifetime is significantly lower than polymer electrolyte and alkaline electrode competitors. The degradation of nickel - a widely used electrode material on the hydrogen/steam side, is severe in the high steam contents found in electrolysers, and is a major source of degradation of the whole cell. While Ni is a vital component in a conventional SOEC fuel electrode, in which it acts as both catalyst and electron conductor, it would be beneficial to find a substitute with better thermal and redox stability to take over the roles of nickel.In this work we seek to build on our prior work on novel composite electrode structures, with a particular focus on utilising nickel exsolved ceria combined into both conventional composites and with our novel electrospun materials to create high performance and durable hydrogen-steam electrodes for solid oxide electrolysers, that will help accelerate their on-going development and deployment, leading to lower cost green hydrogen production.