Research Of LaCo_0.6Ni_0.4O_3-δ As Contact Material And Kinetics Of Pd-containing Cathode For SOFC

Intermediate temperature solid oxide full cell (IT-SOFC) is regarded as an promising research area as its ample material choices in work temperature compared with tradition high temperature solid oxide full cell (SOFC). The contact layers of IT-SOFC are important in the way of collecting electric current and cushioning internal forces especially in those stacks with metal interconnect. However, the reseaches of the contact layer materials are still in the preliminary material selection step, which is far from application. Although Platinum is widely researched as its high electric conduction ability, its high price makes it is impossible for customers afford the product in business market. Thus, finding a material with both good performance and affordable tag price is important for researchers. What’s more, with lower working condition, IT-SOFC cathode faces many problems such as the reduction of catalytic activity. Hence, researches in the area of material performance impact factors and the process of oxygen reduction reaction can help scientists find some theoritical evidence in new electrode composite researches.In this thesis, the researcher optiumizes the preparing technology of LaCo0.6Ni0.4O3-δ (LCN64) perovskite powder and sysnthesized some uniform powder with grain diameter less than100nm in650℃by PVA method. This LCN64pervoskite material has a conductivity which is higher than1250S·cm-1between the temperature of600and800℃and a thermal expansion coefficient wich is17.2×10-6K-1between the temperature of100and900℃. After the single cell test that including five times thermal cycles, the cell with LCN64as contact layer shows steady performance and therfore LCN64can be considered as potential contact layer materials for IT-SOFC.The result of chemistry compatibility test of LCN64and the stainless steel interconnect material SUS430indicates that no secondary phase formed in the sample after keeping in oxide atmosphere at750℃for1000h. However, at the temperature of800℃, some Cr deposites in the place far from SUS430surface after200h constant current test and may replaces some other element in LCN64perovskite.In additon to this, this research find that most electrode reactions are occurred at the surface of PdO cathode and the backbone structure of the electrode has no impact below Td, the decompose temperature of PdO. But when the temperatue is higher that Td, the electrode performace will improved because of the existance of new formed Pd. This phenomenon indicates that Pd has higher ORR catalytic activity than PdO and the reaction determing steps changes.The electrochemical analysis of Pt and Pd as the cathode contact layer materials and YSZ as the cathode demonstrate that these contact layer materials can also impove the oxygen reduction reaction when they contact with the porous electrolyte bone, especially for Pd. When cathode changes from YSZ to Pd-YSZ, Pd is better than Pt as the contact layer because its higher catalytic activity. Furthermore, this outstanding performance of Pd also have impact on the diffusion process in cathode polarization.