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Study On The Perovskite Cathode Of Solid Oxide Fuel Cell

Posted on:2016-11-23Degree:MasterType:Thesis
Country:ChinaCandidate:L H YuFull Text:PDF
GTID:2181330467490983Subject:Chemical Engineering
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Solid oxide fuel cell is an directly convert the chemical energy of fuel into electrical energy with high efficiency and low emission of pollutants and extensive fuel flexibility, and was called the advantage, which is known as the green energy in the21st century. Traditional SOFC was at high temperature (1000℃), because of the high operating temperature, material choice narrow range, cost higher shortcoming which limits the development of it. So developing low temperature solid oxide fuel cell (400-800℃) can greatly reduce the cost of materials, accelerate the commercialization of. But lower the temperature would also reduce the cathode material’s ability to transport oxygen ion, thus developing the IT-SOFC cathode materials become a problem to be solved.The main work includes the following sections:Synthesis and Characterization of Sro.95Tio.o5Cob.9503-δ(A)、Y0.8Cao.2BaCoFe05+δ (B)、Gd1+xBa1+xCo2O5+δ(x=0,±0.05,±0.1)(C)、Sm0.2Ce0.8O1.9(D) were synthesized by a citric acid-nitrates self-propagating combustion method. The chemical compatibility, electrical conductivity and thermal expansion coefficient of the composite cathode were characterized by X-ray diffraction, direct current four-terminal method and thermal dilatometry respectively.In the third chapter Sr0.95Ti0.05Co0.95O3-δ (STC) and electrolyte powders Sm0.2Ce0.8O1.9(SDC) were synthesized by citric acid-nitrates self-propagating combustion method. The composite-cathode was obtained by mixing the STC and SDC powders at a mass ratio of7:3. The chemical compatibility, electrical conductivity and thermal expansion coefficient of the composite cathode were characterized by X-ray diffraction, direct current four-terminal method and thermal dilatometry respectively. X-ray diffraction results show that pure cubic STC perovskite phase can be obtained at900℃and no second phase formed of the composite cathode through the operating temperature. The polarization resistance of the electrode was only0.05Ω·cm at650℃. Anode-supported solid oxide fuel cells of NiO-SDC|SDC|STC-SDC were fabricated. The electrochemical performances were tested at450-650℃using humidified hydrogen as fuel (about3%H2O) and air as oxidant. The results demonstrated that the anode-supported half cells could be sintered at1350℃with a dense electrolyte layer and porous electrodes. Moreover, the single cell with an OCV of0.82V and the maximum power density of721mW cm-2at650℃.In the fourth chapter introduce the Y element doping the perovskite structure of Y0.8Ca0.2BaCo2O5+δ. Cathode materials do have certain ion and electron conductivity, and close match between adjacent components, cobalt is a strategic reserve element, also has the very high electrical conductivity, so a lot of perovskite structure got in-depth research such as cathode materials:SmBaCo2O5+δ、GdBaCo2O5+δ、YBaCo2O5+δ. However, cobalt-based perovskite oxide as a kind of important strategic material has a higher price, and higher TEC caused mismatched with usual electrolytes such as: yttria-stabilized zirconia (YSZ), samaria-doped ceria (SDC) and lanthanum strontium gallium magnesium oxide (LSGM). A-and B-site doping has been widely employed to stabilize YBaCoO3-δ and reduce its TEC. Recently, Gong and Wang reported that Fe doping can bring cathode manageable thermal expansion coefficients as well as fast oxygen incorporation. According to the Y0.8Ca0.2BaCo205+δ and LnBa0.5Sr0.5Co205+δ this experiment preparation and study a new type of perovskite structure of cathode materials Y0.8Ca0.2BaCoFeO5+δ (YCBCF) and study its application in the low temperature solid oxide fuel cell.The fifth chapter study a series of new layered perovskite oxide Gd1+xBa1+xCo2O5+δ (x=0,±0.05,±0.1), and discover the electrical conductivity of the oxide (x=0.1) was higher than some other materials, then further study it in electrochemical performance.
Keywords/Search Tags:IT-SOFC, preparation, cathode material, electrochemical performance
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