【作者】 熊明文；

【导师】 马紫峰；

【作者基本信息】 上海交通大学 ， 应用化学， 2013， 博士

【摘要】 固体氧化物燃料电池研究的主要目标之一是降低操作温度到中温范围（500-700℃），这样不仅可以改善电池组成材料的适配性、延长电池的使用寿命，而且可以降低操作成本，但随着电池工作温度的降低，阴极的极化损失增加会导致电池的性能急剧下降。因此，开发高氧还原活性的阴极材料、降低阴极极化阻抗对中温固体氧化物燃料电池来说至关重要。本文系统地研究了具有钙钛矿结构的DyBaCo₂O_5+δ、不同元素掺杂的DyBaCo₂O_5+δ、 SrCo_1-xGa_xO_3-δ和Pr_xSr_1-xCo_0.9Nb_0.1O_3-δ等钴基材料的物理及电化学性能，旨在寻找热稳定性高且电化学性能好的适合中温固体氧化物燃料电池的阴极材料。分别采用EDTA-柠檬酸法和乙醇超临界干燥辅助EDTA-柠檬酸法制备了DyBaCo₂O_5+δ阴极材料并作为中温固体氧化物燃料电池阴极材料进行了考察。SEM照片显示EDTA-柠檬酸法制备的DyBaCo₂O_5+δ粉体呈现球状颗粒，而乙醇超临界干燥辅助EDTA-柠檬酸法制备DyBaCo₂O_5+δ粉体具有小颗粒组成的绵状结构。650℃时分别以上述两种粉体为阴极材料的单电池的峰值功率密度达到436和529mW cm-2，说明乙醇超临界干燥辅助EDTA-柠檬酸法制备的DyBaCo₂O_5+δ材料的性能更好。为了进一步提高DyBaCo₂O_5+δ的电化学性能，采用EDTA-柠檬酸法分别合成了Dy、Sr和Cu掺杂的Dy1.10BaCo₂O_5+δ、DyBa_0.5Sr_0.5Co₂O_5+δ和DyBaCoCuO_5+δ氧化物材料，并考察了掺杂对DyBaCo₂O_5+δ的结构、热膨胀性能、导电性、材料的表面电子结构和电化学性能的影响。结果表明：Dy1.10BaCo₂O_5+δ、DyBa_0.5Sr_0.5Co₂O_5+δ和DyBaCoCuO_5+δ均具有正交钙钛矿结构，与电解质具有良好的化学兼容性，而且材料表面上吸附氧的浓度均高于DyBaCo₂O_5+δ；30⁸00℃内Dy1.10BaCo₂O_5+δ、DyBa_0.5Sr_0.5Co₂O_5+δ和DyBaCoCuO_5+δ的平均热膨胀系数分别为15.9×10^-6、18.2×10^-6和15.8×10^-6K^-1；与DyBaCo₂O^5+δ相比，Dy1.10BaCo₂O_5+δ和DyBaCoCuO_5+δ的电导率降低，但DyBa_0.5Sr_0.5Co₂O_5+δ的电导率明显增加。上述三种掺杂型材料中，DyBa_0.5Sr_0.5Co₂O_5+δ具有最高电导率和最小极化面电阻，说明掺杂Sr是一种降低阴极极化阻抗、提高氧催化活性的有效方法。通过EDTA-柠檬酸法合成了SrCo_1-xGa_xO_3-δ系列材料并作为中温固体氧化物燃料电池阴极材料进行了评价。结果表明，试样均为钙铁矿结构，随着Ga³⁺含量的增加，热膨胀系数、电导率和阴极材料表面的吸附氧逐渐减小。以面电阻最小的SrCo0.8Ga0.2O3-δ材料为阴极的单电池在650℃时的峰值功率密度为484mWcm-2。采用传统的固相反应法合成了Pr_xSr_1-xCo_0.9Nb_0.1O_3-δ系列材料并对其物理性质及电化学性能进行了考察。结果表明，试样均为钙钛矿结构，材料的电导率和面电阻随着Pr³⁺含量的增加而减小。以面电阻最小的Pr_0.6Sr_0.4Co_0.9Nb_0.1O_3-δ材料为阴极的单电池在650℃时的峰值功率密度为1009mW cm^-2。更多还原

【Abstract】 One of the major goals in solid oxide fuel cell （SOFC） research is to reduce theoperating temperature to intermediate temperature range （500-700℃） in order toimprove the compatibility of the component materials, prolong the lifetime anddecrease the operating costs. However, the reduced working temperature generallyleads to increase of the cathode polarization resistance resulting in drastic decrease inthe cell performance. Development of cathode materials with high catalytic activityfor oxygen reduction and low polarization resistance, therefore, is critical forintermediate-temperature solid oxide fuel cells （IT-SOFCs）. In this thesis, systematicinvestigations on the physical properties and electrochemical performance ofDyBaCo₂O_5+δ，DyBaCo₂O_5+δdoped with different elements, SrCo0.8Ga0.2O3-δandPr0.6Sr0.4Co0.9Nb0.1O3-δmaterials with perovskite structure are discussed in order todevelop novel cobalt-based cathode materials suitable for IT-SOFCs.The DyBaCo₂O_5+δcathode materials synthesized by EDTA-citric acid （EC）sol-gel method and ethanol supercritical drying assisted EDTA-citric acid method（SCEC）, respectively, are investigated as potential cathodes for IT-SOFC. The SEMmorphology images show that the powders synthesized via EC method are sphericalwhereas that obtained by SCEC method have sponge-like shape consisted ofsmall-size and uniform particles. The peak power density of the SOFC withDyBaCo₂O_5+δ（SCEC） as cathode materials reaches529mW cm-2at650℃, while itis436mW cm-2for that with DyBaCo₂O_5+δ（EC） cathode, indicating that synthesismethod has important effect on the cathode performance of DyBaCo₂O_5+δmaterials,and SCEC is preferable than EC to prepare high performance DyBaCo₂O_5+δ. Aimed to improve the electrochemical performance of DyBaCo₂O_5+δ, dopedmaterials of Dy1.10BaCo₂O_5+δ, DyBa_0.5Sr_0.5Co₂O_5+δand DyBaCoCuO5+δoxidepowders were prepared via EC method by introducing Dy, Sr and Cu ions intoDyBaCo₂O_5+δ, respectively, and the properties of thermal expansion, conductivity,surface state as well as electrochemical performance are comparatively evaluated. Theresults demonstrated that all the synthesized materials have an orthorhombicperovskite structure and a good chemical compatibility with electrolyte. Theconcentration of adsorption oxygen on the surface of all these doped materials ishigher than that of DyBaCo₂O_5+δ. The average thermal expansion coefficients, in thetemperature region of30-800℃, of Dy1.10BaCo₂O_5+δ, DyBa_0.5Sr_0.5Co₂O_5+δandDyBaCoCuO5+δare15.9×10-6,18.2×10-6and15.8×10-6K-1, respectively. Theconductivity of Dy1.10BaCo₂O_5+δand DyBaCoCuO5+δis lower than that ofDyBaCo₂O_5+δ, whereas that of DyBa_0.5Sr_0.5Co₂O_5+δis higher. Among the threedoped materials, DyBa_0.5Sr_0.5Co₂O_5+δhas the highest conductivity and minimumpolarization resistance, implying that partial substitution of Sr for Ba in DyBaCo₂O_5+δis an efficient strategy to reduce the polarization resistance and improve the oxygenreduction activity of cathode.The SrCo_1-xGa_xO_3-δoxide powders are synthesized by EC method and evaluatedas cathode materials for IT-SOFCs. The results show that all the samples havebrownmillerite structure. The thermal expansion coefficient, electrical conductivityand the amount of adsorbed oxygen on the surface of the cathode materials decreasegradually with increase in Ga content. The single-cell with SrCo0.8Ga0.2O3-δ, whichhas the lowest area specific resistance among the studied samples, as cathode achievesa maximum power density of484mW cm-2at650℃.The Pr_xSr_1-xCo_0.9Nb_0.1O_3-δpowders are synthesized by traditionalsolid-state reaction method and the physical and electrochemical characteristics areinvestigated. The results show that all the samples have pervoskite structure. Theelectrical conductivity and area specific resistance of the obtained materials decreasewith increase in Pr content. The single-cell with Pr_0.6Sr_0.4Co_0.9Nb_0.1O_3-δ, which hasthe lowest area specific resistance among the studied samples, as cathode achieves a maximum power density of1009mW cm-2at650℃.更多还原