Preparation Research On Anode Modification And Bilayer Electrolyte For IT-SOFC

Solid oxide fuel cells （SOFCs） are considered to be viable sources for powergeneration in the future due to high efficiency, high waste-heat utilization and lowemission of pollutants. At present, many reaserchers pay more attention to improving thecatalytic activity of electrodes and decreasing the operating temperature of SOFCs.Ni/YSZ anode materials are still being developed because of the advantages of low costand easy manufacturability. But the catalytic activity of anode and cell performance areseriously affected due to the agglomeration of Ni catalyst in reducing atmosphere. Thesolution is that adding adequate catalytical metallic oxide could forbid the sintering ofNi particles and increase the power output of cells steadily. In addition, to use someelectrolyte materials with high ionic conductivity for SOFCs is an effective way toreduce the working temperature. The bilayer electrolyte could protect the electrolytefrom the reducing atmosphere and improve the cell performance. So increasing thecatalytic activity of anodes and decreasing the working temperature of SOFCs are studiedin this paper.The impregnation and precipitation method was used to modify NiO powders withCeO₂. Ni-CeO₂/YSZ based unit cells were prepared by aqueous tape casting method dueto low cost，simple operation and pro-environment. The performances of unit cells madeby the two ways were respectively investigated, which were compared with these cellswith adding CeO₂powders directly and without CeO₂. The results showed that themaximum power density of cells having NiO modified with5wt.%CeO₂byimpregnation method was0.94W/cm2, and the polarization resistance was only0.57cm2in3%H2O+H2at750℃. The CeO₂additions by this method could effectivelyprevent Ni particles from sintering and agglomeration, enhance the Ni dispersion on theYSZ framework surface, and improve the electrical performances of cells.GDC powders were prepared by different precipitants. The high yield of GDCpowders could be received by using NH4HCO3as the precipitant. The grains had a littlewide size distribution, but the agglomeration phenomenon was not obvious and the grainmorphology was clear, so the GDC powders could be used to prepare the green tape andobtain the dense GDC electrolyte layer. The relationships between different sinteringtemperatures and cofiring effect of GDC/YSZ layers were studied. The best sinteringtemperature was1450℃. The results showed that the maximum power density ofGDC/YSZ bilayer electrolyte and YSZ based unit cells was0.62W/cm2and0.51W/cm2,and the polarization resistance was0.86cm2and1.2cm2, respectively, in3%H2O+H2 at700℃. At the working temperature of700℃, GDC/YSZ bilayer electrolyte based unitcells had the better electrical performance than YSZ based cells.