Synthesis And Characterization Of New Anode Material For Solid Oxide Fuel Cell

Traditional Solid Oxide Fuel Cell (SOFC) use Ni-yttria stabilzed ziroonia (Ni/YSZ) as its anode material, which leads the operation temperature is high (about 1000℃), and it is difficult for the choice of the electrode material and the cell stack contain materials. This anode has strong dependence of fuel gas, bad tolerance for fuels containing sulfur, and there maybe serious carbon deposit on the anode. LaCrO₃-based materials have high ionic-electronic conductivity, good catalytic and tolerance to sulfur properties. So, the LaCrO₃-based materials are a promising anode in SOFC system which using hydrocarbon as fuel. The above materials was prepared and tested by thermodynamic analysis (TG), differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microcopy (SEM), energy dispersive spectroscopy (EDS), temperature process reduction (TPR), the characterization on the diameters of particles, AC impedance and direct current four-electrode techniques.The La_1-xSr_xCr_1-yMn-yO_3-d(LSCM) anode materials with single phase were identified after sintering above 1250℃for 15h using solid state reaction method. The electrical conductivities of all the LSCM samples increase linearly with temperature over the range of 250℃～850℃in air, and the maximum values is 25S/cm. The conductivities of LSCM7355 sample decrease about two orders of magnitude when the atmosphere changes from air to pure hydrogen and methane, and they are both about 0.2 S/cm in the above reducing atmospheres. The LSCM materials with single phase were obtained after sintering at 1200℃5h using Glycine-Nitrate (GNP) method, and the conductivity of the LSCM materials obtained by GNP method is similar to that of the LSCM materials prepared using solid state reaction method. But it need lower temperature to synthesize materials using GNP method, and the catalytic performance is preferably. For Co element can improve the electrical conductivity of anode materials, so mixed part of Co into LaCrO₃-based materials can increase. the conductivity of anode materials. The La_1-xSr_xCr_1-y-zMn_yCo_xO_3-d (LSCMCo) anode materials were designed and synthesized by GNP method, and the LSCMCo materials with single phase were obtained after sintering at least 1300℃for 5h. Comparing to LSCM materials, the conductivities of the LSCMCo samples did not improve in air, but the conductivities of LSCMCo73541 sample are 0.4S/cm and 4.5S/cm at 850℃in pure hydrogen and methane, respectively. So LSCMCo is more suitable used as anode material of SOFC.The La_0.7Sr_0.3Cr_0.5Mn_0.5O_3-d-Ce_0.8Ca_0.2O_1.8(LSCM-CDC) anode materials with pervskite-fluorite structure were obtained after sintering at 1200℃for 5h by GNP method. The optimum composition of the composite anode of LSCM and CDC was 7 to 3 at molar ratio. At 850℃, the electrical conductivity is 6.49S/cm in air and 1 S/cm in the reduction atmosphere, respectively.The chemical compatibilities between anode (LSCM, LSCMCo) materials and LSGM electrolyte are very good. The above electrode materials but LSCM-CDC have good thermal capabilities with LSGM electrolyte material.