Electrode Material Study And Numerical Simulation For Solid Oxide Fuel Cell

Human beings are confronted with the great challenge for the energy problem in 21 century. Solid Oxide Fuel Cells (SOFC) is an electrochemical reactor, which has the capability of converting chemical energy directly into electricity with high efficiency and low pollution. The traditional electrolyte material based on yttrium-stablized zirconia (YSZ) must be operated at temperatures ranging from 950℃ to 1000℃, due to the relatively high resistivity of the electrolyte at lower temperature. However, lowering the temperature to between 600 and 800℃ has become an inevitable trend for development of SOFC due to the potential benefits it offers, such as cheaper materials, lower degradation problems and becomes a developing trend. So it is important to research and explore electrode material fitting to intermedium temperature solid oxide fuel cell (IT-SOFC).Ce_0.9Gd_0.1O_1.95 (GDC) is a kind of promising electrolyte material, while Ni-Ce_0.8Sm_0.2O_1.9 (Ni-SDC) is a perfect anode material fitting to IT-SOFC. NiO, Ce_0.8Sm_0.2O_1.9 (SDC), NiO-Ce_0.8Sm_0.2O_1.9 (NiO: SDC=1:1 in weight) and Co₃O₄-NiO-Ce_0.8Sm_0.2O_1.9 (Co₃O₄: NiO: SDC=1:1:2 in weight) were synthesized by the combination of sol gel and citric acid-nitrate low temperature self-propagating combustion method. The phase identification of the synthesized powder was measured by X-ray diffraction (XRD). Anode precursors including home-made NiO and SDC have been prepared by different NiO content and fabrication condition, and NiO-SDC and Co₃O₄-NiO-SDC were fabricated into anode precursors respectively. We reduced the anode precursors with pure hydrogen at 820℃ for 2.5 hours, tested the electrical conductivity, and investigated the effect of microstructure on electrical conductivity of Ni-SDC composite anodes. The results show that the anode electrical conductivity depends strongly on the anode microstructure, which is dramatically affected by Ni content and original powder fabrication conditions.The electrical conductivity which is influenced by the NiO is not high enough for the above anode slices. Here, the influence of NiO powder fabrication method for Ni-SDC electrical conductivity was investigated. Two kinds of NiO powder were synthesized with a third kind available in the market. Three types of anode precursors were fabricated with these NiO powders and SDC at the mass rate for 1:1. The electrical conductivity of the anodes was measured and the effect of microstructure was investigated. It was found that the anode electrical conductivity depends strongly on the NiO powder morphologies, particle sizes and microstructure of the cermet anode, which are decided by NiO powder preparation technique. The highest electrical conductivity is obtained for anode cermets with NiO powder synthesized by NiCO₃·2Ni(OH)₂·4H₂O decomposition technique.Doped LaCoO₃ has high ionic and electronic conductivity at lower temperature and is a kind...