Preparation And Examination Of Planar Type Solid Oxide Fuel Cells

Solid oxide fuel cells(SOFC) are expected to become one of the most potential energy sources in 21 century. It is an electrochemical device that converts the energy of a chemical reaction directly into electrical energy. They have high heat efficiency, good fuel adaptiveness, can meet satisfactorily the needs of local supply of power and heat. They will play an important role in our society and economy.Recent SOFC development has been focused on lower temperature operation less than 800℃. Such operation enables us to use low-cost metallic interconnects, long-term cell materials stability, and decrease the materials corrosion for plant components. However, it also increases both the ohmic loss at the solid-state electrolyte and the polarization loss at both electrodes. To reduce the ohmic loss of the electrolyte and the polarization loss of electrodes, two approaches have been conducted in resent years. One is to apply new materials such as La(Sr)Ga(Mg)O₃ or CeO₂ based oxides for electrolytes, which have higher conductivity than that of YSZ at lower temperature, and another is to use a thin film of Y₂O₃ stabilized ZrO₂ (YSZ) to increase the power density at low temperature, this approach is play an important role in the world wide efforts in the field of SOFC.Some works of the preparation of Solid oxide fuel cells such as electrode making, single cell preparation, performance examinations and high-temperature inorganic sealing were attempted in this work. The anode and cathode materials were synthesized and, on this base, a single electrolyte-support and a anode-support planar solid oxide fuel cell with YSZ-Ni |YSZ| LSM configuration were developed, the test system and the fuel control system was fabricated, its electrical performance were examined for operation with H2 as the fuel and the air as the oxidant over a temperature range of 700 to 1000℃.The crystal phases were investigated by X-ray diffraction (XRD). The results showed that the YSZ-NiO powders contained mainly tetragonal ZrO₂. This is because the Y₂O₃ had entered into the clearance of ZrO₂ crystal lattice to stabilize the ZrO₂. The XRD pattern of LSM is very closed to the XRD pattern of nonstoichiometric oxide LaMnO₃.15.The fractured surface morphology of the YSZ-NiO anode, LSM cathode andpositive-electrolyte- negative (PEN) was observed by a scanning electron microscope (SEM). The results showed that the grain sizes of anode and cathode ware a homogeneous microstructure and uniform distribution with porous configuration. About the anode-support SOFC, the average thickness of anode layer, electrolyte layer and cathode layer ware lmm, 0.5mm and 0.15mm. The electrolyte was compact. The element of positive-electrolyte-negative plate (PEN) ware analyzed by fixed-point EDS, the results showed that the infiltration of element in anode and cathode ware impeded by electrolyte. The Sr reacted with ZrCh in electrolyte to become SrZrC>3, which is not conductivity. This is one of the reasons of the bad SOFC's performance.The open-circuit voltage (OCV) of electrolyte-support SOFC was over 1.01 V, the maximum power density at 1000°C reached to 7.73mW/cm2. It was found that the large ohmic losses of the electrolyte was the main factor responsible for the relative low output power density. The relationship between the OCV and operating temperature or the fuel flow rates was also investigated. The results showed that the open-circuit voltage (OCV) of anode-support SOFC was over 0.98 V, the maximum power density at 900°C reached to 3.31mW/cm2.