Preparation And Performance Of The Co-doping Ceria Electrolyte And Doping SrTiO₃ Anode For Solid Oxide Fuel Cell

Solid oxide fuel cells (SOFCs) have attracted worldwide attentions as a electrochemical conversion device for directing fuel stored chemical energy into electricity, because of their high energy conversion efficiency, capability of multi-fuels and simplicity of system design. The key to realize the commercial development of SOFC is to reduce the operating temperature and to lower the manufacturing cost. Traditional SOFC electrolyte and electrode materials show good output powder only at higher temperature. Therefore develop the materials that have good properties at lower temperature becoming a hotspot in current researching.Doping CeO2(DCO) based electrolyte has electrical conductivity one order of magnitude higher than YSZ electrolyte in low temperature range and become a good alternative electrolyte materials for it-SOFC. However, the DCO electrolytes would be partially reduced in reducing atmosphere at high temperature and produce electronic conductivity. This results in the decrease of open-circuit voltage of single cells. Therefore it is necessary to improve the conductivity of DCO electrolyte in the low temperature range while improve its stability at high temperature and in reducing atmosphere. It has been showed that co-doping ceria electrolyte with different rare earth elements can further improve the performance of ceria based electrolyte, and Sc2O3 doping ZrO2 has showed good properties. In the dissertation, CeO2 was co-doped by Sm2O3 and Sc2O3. CSSO electrolyte powders were synthesised by gel-casting method, then prepared the sintered body, and analyzed the microstructures and properties of powders and sintered body samples. The results show that:the CSSO electrolyte powders with single fluorite structure could be synthesized though gel-casting method. The powders have good sintering activity and structure stability, the density of samples sintered at 1500℃ could reach 97% when the content of Sc is 5mol%. The conductivity of Ce0.8Sm0.2-xScxO2-8 samples increased with the increase of Sc content first, and then decreased, the highest conductivity at 600℃ in air can be up to 1.92×10-2 S·cm-1 when the content of Sc is 5mol%. At the same time,the introduction of suitable amount of Sc can improve CSSO sintered body stability in the reducing atmosphere.The performances of anode materials also affect SOFC performances, thus developing new anode materials with good electrochemical activity and stability at operating temperature is also the key to improve SOFC performance. Traditional ceramic metal anode has good electrochemical activity, but its stability in the working conditions is bad, so the SOFC life is not long, especially with the application of hydrocarbons as fuel, perovskite anode attractting the attention of the researchers by its unique superiority, one of the most development potential materials is doped SrTiO3 anode. In this paper, Smo.o4Sro.94Ti1-xScxO3-s powders were prepared through gel-casting method, then prepared the anode and anode symmetric cells, and tested theirs performances. Results show that:Introduction of Sc at Ti position of the Sm0.04Sr0.94TiO3 anode can effectively improve its performance, the sintering activity of Sm0.04Sr0.94Ti1-xScxO3-s powders increased when introduce a small amount of Sc, the total conductivity of Sm0.04Sr0.94Ti1-xScxO3-5 decreased with the increase of Sc concent, but the anodic polarization resistance also decreased, when x=0,0.02,0.04, 0.06, the conductivity of Sm0.04Sr0.94Ti1-xScxO3-δ anode were 41.84 S·cm-1, 39.278·cm-1,32.01Scm-1,19.188·cm-1 respectively at 700℃.The polarization resistance of polarization resistance were 4.869Ω·cm2,4.124Ω·cm2,3.239oΩ·cm2、 2.819Ω·cm2 respectively at 850℃In order to further investigate the application in SOFC of the Ce0.8 Sm0.2-xScxO2-δ electrolyte and Sm0.04Sr0.94Ti1-xScxO3-s anode material prepared in this paper, prepared the Ni-SSDC5/SSDC5/BSCF-SSDC5, Ni-SDC/SDC/BSCF-SDC single cells, and SSTS-SSDC5/SSDC5/BSCF-SSDC5 single cells, then test their performance. Results show that:it could effective improve the open circuit voltage and the output power of single cells though introducing little Sc into SDC. Meanwhile, the SSTS-SSDC5/SSDC5/BSCF-SSDC5 single cells with the anodes content Sc show better properties, it implies that the introduce of Sc could promote the Sm0.04Sr0.94Ti1-xScxO3-s anode materials being used into SOFC.