Energy conversion and storage by means of CO2 and H2O mixtures: development and optimization of reversible solid oxide cells (r-SOCs)

The reduction of pollutants and the use of renewable energy sources are central themes in the historical period we are currently living through. However, some of these sources, such as solar and wind, are intermittent and therefore not always available. In this context, the development of methodologies for converting CO2 and H2O into fuels, such as H2 and hydrocarbons, could be a smart methodology for energy storage and transportation. The possibility to convert carbon dioxide into fuels, helps in reducing the impact of many industrial activities. Reversible solid oxide cells are devices capable of operating both as Fuel Cells and as Electrolytis Cells. They would drive the co-electrolysis of CO2 and H2O in syngas (CO+H2) while working in Electrolysis mode, and then lead to the conversion of the chemical energy into electrical energy by operating in SOFC mode. The design, synthesis, and characterization of electrode materials capable of operating in a reversible cell is necessary from this perspective. However, the reversibility of the material requires the development of highly performing electrode materials in both oxidizing and reducing environments. This thesis focuses on the development and optimization of robust and sustainable electrodes and the creation of a reversible device. As an electrode, a Fe-doped Strontium Molybdate-based perovskite is used comparing two different stoichiometries (Sr2FeMoO6 and Sr2Fe1.5Mo0.5O6), a material that in recent years has gained much interest, as it can be tunable according to the material’s needs and required properties. The synthesis is carried out through the Pechini process (a water-based wet chemistry method) to achieve high purity and controlled insertion of cations into the perovskite structure. The obtained products are characterized using XRD, XPS, SEM, EDX, BET, TPR techniques. To evaluate their stability and reactivity under the operating conditions thermocatalytic tests have been carried out in a quartz reactor (equipped with a GC) to test the behavior in the RWGS reaction. Finally, the Solid Oxide Cell was realized selecting the best electrolyte, and the more adequate electrode ink and the electrochemical activity of the obtained lab-scale device was tested using EIS measurements. The outcomes are promising and interesting differences have been observed between the two compositions.