The Research On Optimization Of SOFC Electrolyte And Anode Microstructure And Testing Of Cathode Performance

Solid oxide fuel cell （SOFC） is a new type of solid-state power generation device.SOFCs are currently attracting the worldwide attention because of high efficiency,environment friendly, strong adaptability to fuel, low cost over other fuel cell types,flexibility in the choice of fuels, the solid structure and no need to use the precious metalcatalyst. Conventional SOFCs are usually operated at high temperature （1000°C） whichcause many problems about materials and techniques.In recent years, researches ofSOFC were mainly concentrated in the low temperature （500～800°C）. With operationtemperature droped, cheap connection materials can be used, thermal cycle stability alsocan be significantly increased and so on. The commercial SOFC will be promoted. Butthe electrolyte ohms resistor and polarization resistor were increased because of loweringoperation temperature, the performance of electrolyte, anodic catalytic activity andmicrostructure must be asked greater demands.In this paper, the electrolyte powder was synthesized through hydrothermal.Synthetic powder was8YSZ by XRD and SEM-EDS testing. The particle of powder andthe agglomeration of powder was very small, which can be known through the TEM. Theproperties of sintering, bending strength and electrochemical performance were studiedthrough adding different amount of α-Al₂O₃to8YSZ. The results showed the optimalα-Al₂O₃content was3wt.%at1450℃, the largest density reached97.72%, the mostbending strength was371.6MPa. NiO-8YSZ anode was prepared by adding8YSZ（3wt.%α-Al₂O₃）to the anode. The results showed bending strength of Ni-8YSZ was301.6MPa, which was more bigger than NiO-8YSZ（0wt.%）.When the content of addingα-Al₂O₃was3wt.%to8YSZ. Its ionic conductivity was the largest at different measuringtemperature points （550～800℃）.The maximum power density of single cell achieved0.97W/cm₂, the minimum ohms resistor （mainly the electrolyte resistance） was0.23Ω·cm₂at750C with H2as the operating gases.The different size of PMMA influence on the microstructure of the anode and cellperformance were studied in this paper. By SEM analysis, the size of pores is proper, theconnectivity among pores was perfect, distributed homogeneously and the microstructurewas improved when the size of PMMA was5μm. By electrochemical test, the minimumpolarization resistance was0.92cm₂and the maximum power density was0.78W/cm₂when the size of PMMA was5μm at750℃with with H2as the operating gases.In this paper, the process of the MIEC cathodic oxygen reduction was studied, theresults showed that the polarization was relevant with the ion and electronic conductivity of the cathode, the materials of cathode, the intrinsic catalytic activity, the microstructureof cathode, the structure of cathode/electrolyte interface and other factors. The studiesshowed the test of the cathode polarization resistance were not demanded highly or thetrend of cathode materials with temperature change was understood, the method ofsymmetric electrode could be used because of simple process and convenient test. Butthe more accurate polarization resistance of cathod need be measured, the method ofthree-electrodes should be used. The value of utmost to real ones could be measured bythe method of three-electrodes because the demand of measuring instrument was so highthat could reduce the measurement error. At500°C,750°C and800°C, the polarizationresistance of SSZ-LSM were53.89cm₂,3.15cm₂and1.05cm₂by the symmetrymethod. The polarization resistance of SSZ-LSM were55.59cm₂,3.03cm₂and0.99cm₂by three-electrode method, the differences among the three were2.30cm₂,0.12cm₂and0.06cm₂.