Oxyanion doping strategies for Solid Oxide Fuel Cell Materials

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).

In terms of the four factors comprising economic impact: knowledge, people, economy, society, this research project will have the following substantial impact. Knowledge The research is aimed at a novel strategy for controlling the performance of solid oxide fuel cell materials, both electrolyte and electrode. The work offers an important new dimension for introducing ionic conductivity into electrode systems, which along with their electronic conductivity, is key to their optimum performance. In addition, in the current SOFC literature there is a growing emphasis on low temperature routes, use of carbon pore-formers, for the production of electrode architectures raising the prospect that such electrodes contain carbonate. Therefore this project will highlight what effect this carbonate has on the performance. People The PhD student and PDRA will gain experience in a number of techniques, leading to two highly qualified researchers for the UK R&D effort in the commercially and politically important area of energy materials. They will have opportunities to present their work at collaborative departments and international conferences, thus aiding in their interpersonal skills, and further promoting the scientific knowledge from the project. In addition, they will be actively involved in public engagement events, improving their skills at interacting with a non-scientific audience. Economy This project will result in the development of a number of new materials, with potential applications as electrolytes or electrodes in solid state electrochemical devices. Examples of such devices include solid oxide fuel cells, electrolysers, hydrogen sensors and separation membranes. The work therefore has significant potential for IP generation. The work will be of interest to industrial R & D labs working in the area of solid state ionics, offering wealth creation at the Universities (through licensing of the IP) and the companies (through exploiting the IP). Society Fuel cells offer tremendous potential for improving energy efficiency and reducing greenhouse gas emissions, with potential applications ranging from transport to stationary power generation. The development of new materials, with improved properties, for use in such applications will result in these systems coming to commercial fruition sooner. As well as leading to wealth generation, as highlighted above, this will help to reduce greenhouse gas emissions, fuel usage, and so has substantial benefits for the environment and hence society in general. Fuel cell devices are also part of the Government's policy towards a low carbon economy, and hence the work is of relevance to the implementation of that policy. The public engagement work performed by the research consortium members will help to promote science to society, helping to highlight the benefits to society of this science, and encourage younger people into scientific study. The research team have demonstrated strong output in this respect from previous research, and has a number of contacts with science centres/museums, such as the Thinktank (Birmingham), where they have held previous demonstrations of fuel cell technology.