Electrospun Mixed Ionic-Electronic Conductors for Energy Applications

Intermediate temperature-solid oxide fuel cells (IT-SOFCs) are under development for operation in the temperature range of 600-800°C. This intermediate temperature negatively affects the electrode kinetics and thus the cell performance, making it essential for the improvement of the electrode materials and architectures. For this reason, high-performance electrolytes and electrodes are currently under development, often based on mixed ionic electronic conductors (MIECs). Due to their ability to carry simultaneously both electrons and oxygen ions, the application of MIECs as IT-SOFC electrodes is expected to extend the electrochemical reaction well inside the electrode thickness. On the other hand, one-dimensional materials like nanotubes, nanorods, and nanofibers have gained significance due to their high surface area and mechanical properties. Electrospinning is the method of choice for nanofiber preparation since, compared to other available methods, is cost-effective, simple, and reproducible. In this work, the manufacture and characterization of nanofiber-based electrodes are investigated. The attention is focused on the preparation and characterization of cathodes for IT-SOFC application, but anodes are investigated as well. The electrode manufacturing process employed is the electrospinning technique. Several electrospun architectures are analyzed, such as co-electrospun and core-shell nanofibers electrodes. Several materials are investigated, the state-of-the-art La0.6Sr0.4MnO3 (LSM) and La0.6Sr0.4Co0.2Fe0.8O3–δ (LSCF), followed by Co-free perovskites such as La0.6Sr0.4Cu0.1Mn0.9O3-δ (LSCuM_1), La0.6Sr0.4Cu0.2Mn0.8O3–δ (LSCuM_2) and La0.6Sr0.4Cu0.2Fe0.8O3–δ (LSCuF). The composite architectures prepared with Ce0.9Gd0.1O1.95 (GDC) are manufactured as well. All the nanofibers are morphologically characterized through SEM and XRD. The electrochemical characterization is carried out through electrochemical impedance spectroscopy (EIS) measurements. The acquired experimental data are fitted through equivalent circuit (EC) modeling, which provides an interpretation of the electrochemical phenomena. Finally, the obtained results are critically compared with literature values.