| Solid oxide fuel cells(SOFCs)have attracted much attention due to their high energy conversion efficiency,fuel flexibility and low emission.SOFCs consist of all solid-state construction elements,thus they are safe and reliable,and have low operation and maintenance costs.Currently,research and development focuses on SOFCs with thin film electrolyte supported on electrodes.The electrode support of the cell can be an anode or a cathode.According to the development of cell materials,anode support designs are widely used,and the most popular one is the Ni-based porous anode support.Although the Ni-based anode has high catalytic activity,its long-term stability(Ni particle coarsening,electrode deformation)has always been a problem that hinders the application of SOFCs technology.Therefore,all-ceramic electrode supported SOFCs have received considerable attention.The performance of SOFCs is usually affected by electrode polarization,including activation polarization and concentration polarization when using high-performance materials and thin electrolyte,especially at reduced operating temperatures.The activation polarization(catalytic activity)is affected by electrode materials and microstructure.The concentration polarization mainly results from the gas transport process which in turn is determined by the pore structure of the electrode support.Therefore,this dissertation is intended to study the ceramic cathode-supported solid oxide fuel cells,focusing on the preparation and surface modification of the cathode support with large straight open pores.Chapter 1 briefly introduces the working principle of solid oxide fuel cells,the development,status and trends of SOFCs technology,and puts forward the research topics and content of this dissertation.In Chapter 2,the La0.8Sr0.2Mn3-δ-Y0.15Zr0.85O2-δ(LSM-YSZ)cathode support was prepared by the phase inversion tape casting method.The as-prepared cathode possessed large straight open pores,and modified with Ce0.8Sm0.2O2-δ(SDC)nanoparticles using the impregnation method.A cathode-supported fuel cell with configuration LSM-YSZ/YSZ/Ni-YSZ was fabricated,and tested by exposing its anode to H2 fuel(humidified with 3 vol.%H2O)at a flow rate of 30 seem and the cathode to the ambient air.The cell with the SDC-modified cathode attained maximum power densities of 270,395,541 mW cm-2 at 750,800,and 850 ℃,respectively,which were 3.1,2.8,and 2.4 times higher than the corresponding values for the cell with the un-modified cathode.Chapter 3 is concerned with the study of SOFCs supported on La0.6Sr0.4Fe3-δ-Gd0.iCe0.9O1.95-δ(LSF-GDC)cathode.The cathode with large straight open pores was prepared by the phase inversion tape casting,and was modified with La0.6Sr0.4CoO3-δnanoparticles using the impregnation method.A SOFC with configuration LSF-GDC/GDC/NiO-GDC was fabricated,and its electrochemical performance tested.The cell with the LSC-modified cathode exhibited maximum power densities of 366,567,726 mW cm-2 at 650,700,and 750 0C,respectively,which were 3.7,3.1,and 2.4 times higher than the corresponding values for the cell with the un-modified cathode.In Chapter 4,the researches presented in this dissertation are summarized,and further research needs are identified. |
