| Solid Oxide Fuel Cells (SOFC) was considered as a promising fuel cell because of its higher energy efficiency, rapid electrode kinetics without using expensive electrocatalysts such as Pt, the possibility of processing CO, CH4 and other Carbon based fuels, and flexibility to stacks of cells. Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFCs) become a leading trend for development of SOFC. However, lowering the temperature leads to the increasing of electrode polarization loss. So it is important to research and explore electrode materials with high performance to meet the requirement of IT-SOFCs. A2BO4 type oxide materials exhibited suitable thermal expansion coefficient (TEC), which can match reasonably well with the CGO or LSGM electrolyte materials. And in the temperature range of 600～800oC, this material showed higher oxygen diffusion and surface exchange coefficients than the traditional LSCF system. All these results imply that A2BO4 type oxide is a kind of promising cathode materials for IT-SOFCs.In this thesis, cathode materials Ln2-xCexCuO4(Ln=La,Nd,Sm) for IT-SOFCs were prepared by glycine-nitrate process (GNP). The chemical compatibility of the electrode and electrolyte at high temperature and effects of the sintering temperature on the microstructure and electrochemical properties were investigated, respectively. The results showed that maximum solubility of Ce in the La2-xCexCuO4 is 3% and the maximum solubility of Ce in the Nd2-xCexCuO4 and Sm2-xCexCuO4 is 20%. The electrode materials and the electrolyte CGO have good chemical compatibility at 1050 oC. The microstructure of the electrode sintered at 1000oC showed a structure with reasonable porosity and well-necked particles. The good adhesion between electrode and electrolyte is also observed. The doping of Ce increased the conductivity of these materials. The conductivities of Nd2-xCexCuO4 and Sm2-xCexCuO4 exceed 60 S/cm in the intermediate temperature range of 500～750oC. Sm2-xCexCuO4 system exhibited the highest performance. When the doping content of Ce is 20%, the electrode gave the lowest polarization resistance (0.37Ω.cm2) at 750 oC in air. Oxygen partial pressure effect experiments have been performed to study the mechanism of the reaction occurred on the electrode. We have studied variations of the electrode polarization resistance with temperatures and oxygen partial pressures, respectively. The results showed that the possible rate limiting step for cathode reaction depends on the charge transfer process, oxygen adsorption-desorption process and oxygen ion transfer from the TPB to the CGO electrolyte process. The rate limiting step for Sm1.8Ce0.2CuO4 cathode is the charge transfer process.In order to improve the electrode property further, the composite cathode of Sm1.8Ce0.2CuO4-CGO (SCC-CGO) and Sm1.8Ce0.2CuO4-Ag (SCC-Ag) electrodes were studied systematically. The results showed that the addition of CGO powders into SCC electrode was effective in improving the electrode performance and the bonding of the electrode and electrolyte. The addition of 5 wt.% CGO in SCC resulted in the lowest polarization resistance of 0.17 ?.cm2 at 750 oC in air. And the polarization phenomenon of the cathode was improved simultaneously. When the current density reached 150 mA.cm-2, the over-potential is 30 mV at 750 oC in air. The SCC-Ag composite cathode also showed fine electrochemical performance. The addition of 5 wt.% Ag in SCC resulted in the lowest polarization resistance of 0.18 ?.cm2 at 750 oC in air.Besides, the A2BO4 type manganate cathode materials, Sr2-xLaxMnO4 and Sr1.5LaxMnO4, were also prepared. The electrochemical properties of these materials were studied as used for SOFC cathode. The results showed that Sr1.5LaxMnO4 cathode exhibited improved performance. The lowest polarization resistance (0.25 ?.cm2) was obtained for Sr1.5La0.35MnO4 at 750 oC in air. Study on the oxygen reduction mechanism of Sr1.5La0.35MnO4 electrode showed that the rate limiting step changed with the variation of temperature and PO2.
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