Oxyanion doping strategies for Solid Oxide Fuel Cell Materials

为了提高能源效率和减少温室气体排放，燃料电池技术的应用得到了越来越多的支持，它提供了从运输到固定发电的应用潜力。许多不同的燃料电池系统已经被研究过，电解质是决定运行温度的关键。在高温系统（50 ~ 500℃）方面，采用陶瓷电解质，这种固体氧化物燃料电池（sofc）在燃料灵活性和效率方面具有许多优点。SOFC的一个关键要求是具有良好的离子（氧化物离子或质子）导体作为电解质，这推动了对新型氧化物离子和质子导电系统以及相关电极材料的大量研究。在电极材料方面，典型的钙钛矿相关的过渡金属包含系统是阴极的目标。该领域的研究表明，除了材料的体积特性外，电极的微观结构对于确保最佳性能至关重要。这导致了对纳米级电极结构设计的大量研究，利用低温合成技术和碳基成孔剂。然而，一个尚未被考虑的特征是，这些策略很可能将残余碳酸盐引入电极。由于假设C太小而无法容纳在电极材料的晶体结构中，这一特征大多被忽视了。然而，事实并非如此，事实上，高温铜超导体领域的研究表明，钙钛矿结构可以容纳碳酸盐和一系列其他氧阴离子（硫酸盐、磷酸盐、硼酸盐）。因此，有必要研究低温合成SOFC电极材料的碳酸盐含量，并研究其对性能的影响。此外，正如我们小组最近在磷酸盐掺杂电解质材料上所做的工作所表明的那样，通过加入碳酸盐或其他氧阴离子，有可能开发出具有改进性能的新材料。因此，在这个项目中，将研究氧阴离子掺杂到一系列SOFC电极和电解质材料中的可能性，从钙钛矿系统开始，然后扩展到萤石材料的研究。在碳酸盐掺入的情况下，这将通过有机前体的低温合成来实现，而在硫酸盐和磷酸盐的情况下，低温和高温合成策略将被采用（特别是磷酸盐更热稳定，允许更高温度的合成策略）。

The drive for increasing energy efficiency and reducing greenhouse gas emissions has garnered increasing support for the use of fuel cell technology, which offers the potential for applications ranging from transport to stationary power generation. A number of different fuel cell systems have been investigated, with the electrolyte being crucial in dictating the temperature of operation. In terms of high temperature systems (>500C), a ceramic electrolyte is employed, and such solid oxide fuel cells (SOFCs) offer many benefits in terms of fuel flexibility and efficiency. A key requirement for an SOFC is a good ionic (oxide ion or proton) conductor as the electrolyte, and this has driven considerable research into the development of new oxide ion and proton conducting systems, along with accompanying electrode materials. In terms of the electrode materials, typically perovskite-related transition metal containing systems are targeted for the cathode. Research in this area has shown that in addition to the bulk characteristics of the material, the microstructure of the electrode is vitally important in ensuring optimum performance. This has led to considerable research into the design of nano-scale electrode structures, utilising low temperature synthesis techniques and carbon-based pore-formers. However, a feature that has not been considered is the fact that these strategies are likely to introduce residual carbonate into the electrode. This feature has been mostly overlooked due to the assumption that C is too small to be accommodated in the crystal structure of the electrode material. However, this is not necessarily the case, and indeed research from the high temperature cuprate superconductor area has shown that the perovskite structure will accommodate carbonate and a range of other oxyanions (sulphate, phosphate, borate). There is therefore a clear need to investigate the carbonate content of low temperature synthesised SOFC electrode materials, and examine how this affects the performance. In addition there is the potential to develop new materials with improved properties through the incorporation of carbonate or other oxyanions, as shown by recent work from our group on phosphate-doped electrolyte materials. In this project therefore, the possibility of oxyanion doping into a range of SOFC electrode and electrolyte materials will be examined, starting with perovskite systems, and then extending to investigate fluorite materials. In the case of carbonate incorporation, this will be achieved through low temperature synthesis from organic precursors, while in the case of sulphate and phosphate, both low and high temperature synthesis strategies will be employed (phosphate in particular is more thermally stable, allowing higher temperature synthesis strategies).