【作者】 吕洪；

【导师】 胡克鳌；

【作者基本信息】 上海交通大学 ， 材料学， 2007， 博士

【摘要】 本文以中温固体氧化物燃料电池（IT-SOFC）为背景,紧密追踪当前研究热点,探索替代Ni基金属陶瓷的新型阳极材料,系统研究了新型阳极材料与La_0.8Sr_0.2Ga_0.8Mg_0.2O_3-δ（LSGM）的热相容性,阳极材料在氢气中的电化学性能以及在甲烷中的电化学性能;同时,为解决阴极材料热膨胀系数与电解质不匹配的问题,本文也在探索新型阴极材料方面做了一些工作;最后,采用性能较好的新型阳极材料和阴极材料制备成单电池进行发电试验。本课题对于解决SOFC获得实际应用并推向市场面临的关键问题具有非常重要的意义,研究结果为SOFC新型电极材料的研究提供有价值的参考信息。本文以CeO₂为基体,利用柠檬酸-硝酸盐燃烧法合成过渡金属元素（Mn、Co、Fe、Cu、Ni）掺杂氧化铈固溶体,系统研究了固溶体的固溶度范围,在氧化气氛和还原气氛中的高温稳定性。研究表明,过渡金属元素在CeO₂中的固溶度一般为0.1～0.2,固溶体在不同气氛中具有良好的稳定性。Ce_1-xTm_xO_2-δ固溶体的作为阳极材料,在热膨胀系数、化学相容性方面与电解质LSGM的匹配性良好,Ce₍1-x_Tm_xO_2-δ固溶体具有氧化氢气能力,随着掺杂量的增加,催化能力增强;对于不同的气体成分,在H2+3%H₂O的催化能力强于在干氢气中。Ce_0.9Fe_0.1O_2-δ和Ce_0.8Fe_0.2O_2-δ在湿氢中700℃的极化电阻分别是0.975（Ωcm²）和0.577（Ωcm²）,作为IT-SOFC的阳极材料,具有一定的可行性,有望成为适合LSGM电解质的阳极材料。同时,Ce_1-xFe_xO_2-δ阳极有直接氧化甲烷的能力,Fe掺杂量越高,对甲烷的氧化能力越强;在加湿甲烷气氛中,在700℃下,Ce_0.9Fe_0.1O_2-δ的极化电阻为2.25Ωcm²,Ce_0.8Fe_0.2O_2-δ的极化电阻为1.27Ωcm²,有希望成为新型直接氧化甲烷固体氧化物燃料电池的阳极材料。本文对Fe,Mn分别掺杂Sm_0.5Sr_0.5CoO₃新型阴极材料的晶体结构,热膨胀系数,电导率及电化学性能进行了系统研究。Sm_0.5Sr_0.5Mn_xCo_1-xO_3-δ体系化合物都是正交晶系钙钛矿结构;随着Mn取代量的增加,SSC的热膨胀系数被显著降低,电导率减小,极化电阻增加。在高Mn含量时可以获得良好的热膨胀系数匹配,但是只有在低Mn含量才可以获得较高的电导率和较低的极化电阻。因此,作为中温固体氧化物的阴极材料, SSMC体系并不十分适合。Sm_0.5Sr_0.5Co_1-xFe_xO_3-δ随着Fe取代量的不同,SSCF的晶体结构发生变化,在0≤x≤0.4时,SSCF为正交晶系钙钛矿结构,在0.5≤x≤0.9时,SSCF为立方晶系钙钛矿结构。Fe掺杂可以降低Sm_0.5Sr_0.5CoO₃的热膨胀系数,随着Fe含量的增加,热膨胀系数减小。在800℃下,SSCF导电率均大于100 S /cm。随着Fe含量的增加,极化电阻增大;当Fe的含量达到0.4时,极化电阻达到最大值;之后,随Fe含量的增加,极化电阻减小,在700～800℃时,Sm_0.5Sr_0.5Co_0.2Fe_0.8O_3-δ表现出了良好的氧催化活性,因此,有可能发展成为中温固体氧化物燃料电池的阴极材料。本文最后对电解质支撑型Ce_0.8Fe_0.2O_2-δ/LSGM/Sm_0.5Sr_0.5Fe_0.8Co_0.2O_3-δ单电池发电性能进行了研究。在采用H₂+3%H₂O作为燃料时,单电池在700～800℃的开路电压（OCV）为1.198～1.185V,800℃时的最大功率密度为98mw/cm2,高于较采用相同结构的Ni基金属陶瓷阳极材料的单电池功率密度。因此,Ce_0.8Fe_0.2O_2-δ和Sm_0.5Sr_0.5Fe_0.8Co_0.2O_3-δ可以作为具有应用前景的中温固体氧化物燃料电池的新型电极材料。在采用CH4+3%H2O作为燃料时,单电池在800℃时,电池的开路电压为1.189V,最大功率密度为52.2mw/cm²,在高温下长期运行过程中,电池的开路电压略有下降,同时,阳极极化电阻变化不大,电池运行后,阳极表面碳元素量较少,说明Ce_0.8Fe_0.2O_2-δ具有抗积炭的能力。因此,Ce_0.8Fe_0.2O_2-δ作为中温直接甲烷氧化物燃料电池的新型阳极材料具有一定的应用价值。更多还原

【Abstract】 The core materials of SOFC are electrolyte, anode and cathode. La_0.8Sr_0.2Ga_0.8Mg_0.2O_3-δ（LSGM） is the promising electrolyte for IT-SOFC, however, the electrolyte is restricted to apply because of the reaction with Ni cermet. Ce_1-xTm_xO（2-δ）（Tm= Mn, Co, Fe, Cu, Ni） have been investigated in order to searching the novel anode, which could be suited with the LSGM electrolyte. We also research the electrochemical behavior of Ce_1-xFe_xO_2-δ as a possible SOFC anode materials for the direct oxidation of methane. At same time, a novel cathode material have been investigated. At last, a single solid oxide fuel cell is prepared with the novel anode and cathode running on hydrogen or methane in this thesis.The solid solubility limit, crystal structure, thermal expansion rate, and electrochemical performance of Ce_1-xTm_xO（2-δ）（Tm= Mn, Co, Fe, Cu, Ni） have been investigated. Ce_1-xTm_xO（2-δ） have been synthesized by the citrate method. The solid solubility limit of the Ce_1-xTm_xO（2-δ） is about 0.1⁰.2. The solid solution has a cubic symmetry. The electrochemical behavior of anode has been analyzed by electrochemical impedance spectroscopy. Ce_1-xTm_xO（2-δ） have a significant effect on the electrochemical oxidation of hydrogen at these temperatures（550⁷00℃）, the polarization resistance decreases with increasing doping element content while the lower polarization resistances appear in humidified H2 than in dry H2. The polarization resistances of Ce_0.9Fe_0.1O_2-δand Ce0.8Fe0.2O2-δrespectively show 0.975 ?cm2 and 0.577?cm2 in humidified H2 at 700℃. Therefore, Ce_1-xFe_xO_2-δ （x=0.1, 0.2） will be a promising candidate for IT-SOFC anode material. Second, the catalytic activity for direct oxidation of dry methane and long-term performance stability of Ce_1-xFe_xO_2-δ （FDC, x=0.1, 0.2） have been investigated. Ce_1-xFe_xO_2-δ （x=0.1, 0.2） has shown the properties of rapid direct electrochemical oxidation of methane at these temperatures（550⁷00℃）, the polarization resistance decreases with increasing Fe content. The polarization resistances of Ce_0.9Fe_0.1O_2-δand Ce0.8Fe0.2O2-δrespectively show 2.25Ωcm² and 1.27Ωcm² in humidified CH4 at 700℃.Therefore, Ce_1-xFe_xO_2-δ （x=0.1, 0.2） will be a promising candidate for IT-SOFC anode material to direct oxidate dry methane.The crystal structure, thermal expansion rate, electrical conductivity and electrochemical performance of Sm0.5Sr0.5MxCo1-xO3 -δ（M=Fe, Mn） have been investigated. Two crystal structures have been observed in the specimens of Sm0.5Sr0.5FexCo1-xO3-δ（SSFC） at room temperature, the perovskite structure of SSFC has an Orthorhombic symmetry for 0≤x≤0.4 and a cubic symmetry for 0.5≤x≤0.9. The specimens of Sm0.5Sr0.5MnxCo1-xO3-δ（SSMC） crystallize in an Orthorhombic structure. The adjustment of thermal expansion rate to electrolyte, which is one of the main problems of SSC, can be achieved to lower TEC values with more Fe and Mn substitution. Especially, Sm0.5Sr0.5Mn0.8Co0.2O3-δexhibits good thermal compatibility with La0.8Sr0.2Ga0.8Mg0.2O3. The polarization resistance increases with increasing Mn content, Nevertheless, the polarization resistance of SSFC increases with increasing Fe content, but when the amount of Fe reaches to 0.4, the maximum is obtained while the resistance will decrease when the amount of Fe reaches above 0.4. Sm0.5Sr0.5Fe0.8Co0.2O3-δelectrode exhibits high catalytic activity for oxygen reduction operating at temperature from 700 to 800℃.A single solid oxide fuel cell is prepared with the novel anode （Ce0.8Fe0.2O2-δ） and cathode （Sm0.5Sr0.5Fe0.8Co0.2O3-δ） running on hydrogen or methane. The maximal power density is 98mw/cm2 running on humidity hydrogen at 800℃. The maximal power density is 52.2mw/cm2 running on humidity methane at 800℃. Moreover, very little carbon is detected on the anode, suggesting that carbon deposition was limited during cell operating.更多还原