Preparation And Characterization Of Cathode Materials For Solid Oxide Fuel Cells

Substantial efforts are under way to reduce the working temperature of solid oxide fuel cell (SOFC),400-800℃will greatly reduce the cost of the battery, speed up the marketization and commercialization.But the electrochemical activity of the cathode dramatically decreases with decreasing temperature, so the development of cold cathode materials is a problem to be solved.The main work includes the following sections:Synthesis and Characterization of La0.8-xPrxSr0.2FeO3+δ for cathodes:Perovskite-type La0.8-xPrxSr0.2FeO3+δ(x=0.0,0.2,0.4,0.6)solid solution powders and electrolyte BaCe0.7Zr0.1Y0.2O3(BCZY)and Sm0.2Ce0.8O1.9(SDC) were synthesized by a citric acid-nitrates self-propagating combustion method. The synthesized samples that sintered at950℃for3h are single perovskite phase. The electrical conductivities of sintered ceramics at450～800℃were measured by four-probe technique. An anode-supported fuel cell consisting of Ni-BCZY|BCZY|LPSF4-SDC by the quality of3:2ratio of LPSF4and SDC was fabricated, the obtained single cells were tested that a low polarization resistance of the electrodes of0.07Ω·cm2, respectively, a high open-circuit potential of0.90V and a maximum power density of415mW·cm-2were achieved at700℃. This investigation indicated that the LPSF4-SDCcomposite-cathode could be a potential candidate for IT-SOFCs.Electrochemical Performance of SmBaCo2O5+δ-Sm0.2Ce0.8O1.9as Composite-cathode:The cathode powders of double perovskites-type SmBaCo2O5+δ(SBCO) and electrolyte powders of fluorite-structure Sm0.2Ce0.8O1.9(SDC) were synthesized by a citric acid-nitrates self-propagating combustion method. The composite-cathode was obtained by mixing and grinding SBCO and SDC powders at the ratio of3:2(wt%). The results indicated that there were no interactions between SBCO and SDC in1000℃for2h. The electrical conductivity of the SBCO-SDC composite-cathode reached to369～234S/cm at450℃～800℃. The addition of SDC decreased the TEC of the composite-cathode. The single cell has ideal microstructure and good interface between anode, electrolyte and cathode. At650℃, the polarization resistance of the electrodes was0.031Ω·cm2. A0.77V of open-circuit potential and a640mW·cm-2of maximum output power density were obtained at650℃by using humidified (～3% H2O) hydrogen as fuel and air as oxidant. The results presented here demonstrated that the SBCO-SDC composite-cathode could be used as a potential candidate cathode for IT-SOFCs.Synthesis and Characterization of Sm1-xYxBaCo2O5+δ for cathodes: Sm1-xYxBaCo2O5+δ(x=0.0,0.25,0.5,0.75,1.0)solid solution powders and electrolyte Sm0.2Ce0.8O1.9(SDC)were synthesized by a citric acid-nitrates self-propagating combustion method. The electrical conductivities of sintered ceramics at450～800℃were measured by four-probe technique. The composite-cathode was obtained by mixing and grindingSYBC5and SDC powders at the ratio of3:2(wt%). An anode-supported fuel cell consisting of Ni-SDC|SDCY|SYBC5-SDC was fabricated, the obtained single cells were tested that a low polarization resistance of the electrodes of0.028Ω·cm2, respectively, a high open-circuit potential of0.77V and a maximum power density of524mW·cm-2were achieved at650℃. This investigation indicated that the SYBC5-SDC composite-cathode could be a potential candidate for IT-SOFCs.Synthesis and Characterization of Sm0.5Pr0.5BaCo2O5+δ for cathodes:The cathode powders of Sm0.5Pr0.5BaCo2O5+δ (SPBC)and electrolyte powders of fluorite-structure Sm0.2Ce0.8O1.9(SDC) were synthesized by a citric acid-nitrates self-propagating combustion method. An anode-supported fuel cell consisting of Ni-SDC|SDC|SPBC was fabricated, the obtained single cells were tested that a low polarization resistance of the electrodes of0.040Ω·cm2, respectively, a high open-circuit potential of0.74V and a maximum power density of494mW·cm-2were achieved at650℃. This investigation indicated that the SYBC5-SDC composite-cathode could be a potential candidate for IT-SOFCs.