Currently, the search for an improvement in the anode performance is focused in two main areas: improvement by optimising the Ni-YSZ cermet anode properties or improvement through the use of new materials. As for the first line, porosity is one of the factor s responsible for the properties because it controls both the transport of gas fuel to the reaction sites as well as the size of the triple phase boundary (TPB). This zone is defined as the interface between electrode, electrolyte and gas reactants.
Current materials generally do not present enough porosity at high temperatures and therefore the surface area is small. In this respect, a number of authors have tried to improve porosity by introducing certain additives to the anode and thus modify the synthesis conditions. However, there is no precise control over the final porosity. Therefore, we propose a relatively novel route in this project, to control precisely the microstructure, which consists in the use of materials with high porosity in an ordered arrangement. Such 3D matrix of meso and macroporous of organic materials like poly(methyl methacrylate) (PMMA),that might be used afterwards as a template to insert a solution containing the anode and/or the catalysts to then being removed by the appropriate thermal treatment. After this process, we will obtain a material presenting the original arrangement of the pores.
This control over the microstructure should imply a significant improvement in the performance and consequently, it might probably allow a reduction in the operating temperatures of the current fuel cells. As for the search of new materials, mixed oxide materials promise an improvement over YSZ cermets, especially due to the "ability" of transition metals to present multiple oxidation states. In fact, a perovskite-based anode material developed in our research group, La0.75Sr0.25Cr0.5Mn0.5O3-del shows comparable electrochemical performance to Ni/YSZ and, furthermore, improving the catalytic activity.
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