【作者】 刘立敏；

【导师】 孙克宁；

【作者基本信息】 哈尔滨工业大学 ， 化学工程与技术， 2012， 博士

【摘要】 固体氧化物燃料电池（SOFC）由于自身众多优点而正成为燃料电池的主流方向。然而，在走向实用化进程中，还有若干问题需要解决。首先，尽管SOFC与其他类型的燃料电池相比，具有燃料适应性强、Ni基阳极催化性能优异等优点，但廉价易得的碳氢化合物燃料易使SOFC发生碳沉积和硫毒化。Ni基阳极抗积碳、耐硫毒化能力差，这直接限制了其在直接碳氢燃料电池中的应用。这个问题虽经长期研究但一直没得到很好的解决。其次，目前SOFC的燃料仍以氢气为主，而氢气无论是存储还是运输都存在很大困难。对于商业化中小型、便携式的分散电源，应首选液体燃料或易液化的燃料以便运输和存储。针对以上问题，本论文开展了SOFC新型阳极的制备和改性研究，主要进行了阳极的耐硫抗积碳性能及以液氨为燃料的SOFC阳极材料的探索，同时对新结构的对称电池电极材料及电池性能作了初步的研究。研究了BaO对传统Ni-YSZ基阳极SOFC耐硫性能的影响：以Ni/YSZ为SOFC的阳极材料，YSZ为电解质，通过流延法制备阳极支撑电池，采用浸渍法把BaO引入到Ni/YSZ阳极上。利用甘氨酸瞬间火焰燃烧使BaO粒子达到纳米尺度。使用含不同浓度H₂S的湿氢气为燃料考察BaO对传统Ni基SOFC耐硫性能的影响。EDS结果表明电池阳极中BaO的含量约为5%。电池恒流放电测试表明当燃料从氢气切换到浓度为50ppmH₂S的湿氢气时，电池功率密度没有明显变化，即没有观察到传统Ni基阳极在通入硫化氢后的明显电压降。湿氢气中H₂S浓度从5逐渐变化到50ppm时，电池放电性能保持了良好的稳定性。在800oC时功率密度可达963mW·cm-2。EDS和XPS结果显示在硫毒化测试后没有硫污染电池阳极。实验结果表明：BaO/Ni界面不仅具有优良的抗积碳性能同时也具有良好的耐硫毒化能力。进行了稀土双掺杂Ni基CeO₂阳极的抗积碳耐硫毒化能力的研究：采用Y和Yb对CeO₂进行双掺杂来研究稀土协同作用对材料耐硫抗积碳性能的影响。采用甘氨酸燃烧法制备超细Ce_0.8YxYb_0.2-xO_1.9（x=0，0.1，0.2）、GDC（Ce0.9Gd0.1O1.95）粉体，对材料进行XRD、EDS、SEM、电导率和热性能测试。制备了GDC电解质支撑，Ni-Ce_0.8Y_0.1Yb_0.1O_1.9、Ni-Ce_0.8Y（0.2）O_1.9、Ni-Ce_0.8Yb_0.2O_1.9分别为阳极、Ce_0.9Gd_0.1O_1.95+La_0.6r_0.4Co_0.2Fe_0.8O₃-δ（GDC+LSCF）为阴极的全电池。电化学测试表明：Ni-Ce_0.8Y_0.1Yb_0.1O_1.9在750oC以干甲烷为燃料时，以200mA·cm-2恒流放电120小时功率输出无衰减，而传统的Ni-YSZ阳极以甲烷为燃料时出现了严重的积碳现象。此阳极在700oC以下，H₂S浓度为5ppm和20ppm时，性能衰2EDS结果表明：测试后Ni-Ce_0.8Y_0.1Yb_0.1O_1.9阳极无碳沉积也未检出硫及硫化物。表明对于直接碳氢燃料电池，稀土共掺杂CeO₂/Ni阳极是一种很有吸引力的阳极材料。研究以氨为燃料的SOFC阳极的制备与电化学性能：本章采用电导率较高的SSZ做电解质，流延法制备Ni-YSZ|Ni-SSZ|SSZ半电池，采用浸渍法向Ni/SSZ功能层中引入Fe制备了电池Fe-Ni-YSZ|Fe-Ni-SSZ|SSZ|LSM-SSZ并进行了电化学性能测试。同时用同种方法制备未掺铁的SOFC电池。测试结果表明：Fe的引入可以提高电池的性能。使用氨气作为燃料时竟获得了比纯氢气为燃料时更高的功率密度。考虑到电解质可以做得更薄及Fe/Ni对氨的良好催化活性，Fe/Ni基阳极将是很好的氨燃料电池阳极材料。对新型SOFC对称电池电极材料及电池性能进行了初步探索：本章采用掺杂的CeO₂-LaFeO₃作为对称电池的阴阳极，Sc_0.1Zr_0.9O_1.95（SSZ）作为电解质构建对称电池，掺杂的CeO₂-LaFeO₃作为对称电池电极的结构可行性和电化学性能得到了详细的评估和验证。结果证明：在长时间放电测试后发现有Fe和MnO从体相材料中析出，而Fe和MnO的析出有利于电池性能的提高而不是性能下降。在氢气气氛下恒流放电120h后，电池输出功率提高了8%。EIS测试表明电池的极化电阻随着电流的增加而减小。更多还原

【Abstract】 Solid oxide fuel cells （SOFCs） are the interesting topic due to the obvious merits.It is the challenge for the existing fuel cell technologies to provide a commercialpath. The system costs and fuel infrastructures are the main critical bottlenecks. Oneof the merits of the SOFCs is the good fuel flexibility. Therefore, many gases, suchas hydrocarbon, can be used as the fuels. However, the investigation of the practicalsystem has been still hampered by some problems, such as the coking on thewell-known conventional nickel-based anode once using hydrocarbon fuel such asmethane or propane that the occurance of severe degradation will compromise thecell performance. During the current time, SOFCs are being directly oriented to theportable devices, which require liquid fuel favorable for SOFC operation. Accordingto the above problems, we concentrated on the anodes which can work steadily withtolerance to sulfur and coking for a long time and the anodes which are suitable forammonia-fueled SOFC. At the same time, we studied some materials which can beused as the symmetrical electrode.The sulfur tolerance improvement of Ni-YSZ anode by alkaline earth metal oxideBaO for solid oxide fuel cells was studied: The anodic performance of Ni-Y2O3stabilized ZrO2（Ni-YSZ） modified by alkaline earth metal oxide BaO wasinvestigated for solid oxide fuel cells operating in H₂S-containing hydrogen fuels.The EDS results indicated that the amount of BaO was about5%. The cell withBaO/Ni-YSZ anode exhibited almost constant peak power densities when the fuelwas switched from wet hydrogen to50ppm H₂S contaminated wet hydrogen andgood stability in wet H₂S-contained hydrogen fuels with H₂S concentrationgradually increased from5to50ppm. The EDS and XPS results demonstrated thatno element S was detectable after sulfur poisoning testing. High water adsorptionability of BaO could be the primary reason for the high sulfur tolerance. Theobtained results confirmed the previous conclusion that BaO/Ni interfaces can resistnot only deactivation by coking but also sulfur poisoning of a conventional Ni-YSZanode.The enhanced sulfur and carbon coking tolerance of novel Co-doped Ceria basedanode for solid oxide fuel cells were concentrated: Doubly doped CeO₂based anodewith Y and Yb was considered for direct methane solid oxide fuel cells. The poweroutput of the cell with Ni-Ce_0.8Y_0.1Yb_0.1O_1.9anode and stability at varioustemperatures were investigated when air was used as oxidant and pure H₂,5ppmH₂S containing H₂and dry CH₄as fuel, respectively. At750oC, the cell displayedstable power output for120h at200mA cm-2when fueled with dry CH₄, suggesting the carbon deposit was largely absent on the anode, which was confirmed by theSEM observation and EDS results. The results also proved that the rare earthelements Y and Yb affected the sulfur tolerance performance of the anode in acooperative fashion leading to good anode stability in the contaminated fuel. TheSEM and EDS results provided evidence that the cell with Ni-Ce_0.8Y_0.1Yb_0.1O_1.9anode was tolerant toward the H₂S contamination. The remarkable performancessuggested that co-doped CeO₂anode was an attractive electrode component fordirect hydrocarbon solid oxide fuel cells and might also be used as a catalyst forreforming of hydrocarbon fuels and for removal of fuel gas contaminations such assulfur.The improved performance of ammonia-fueled solid oxide fuel cell with SSZ thinfilm electrolyte and Ni-SSZ anode functional layer was investigated: Ammoniaoffers several advantages over hydrogen as an alternative fuel. However, usingammonia as a hydrogen source for fuel cells has not been received enough attentions.In this chapter, Scandia-stabilized Zirconia （SSZ） thin film electrolyte and Ni-SSZanode functional layer were developed by tape casting in order to obtain high poweroutput performance in ammonia, the results of a SOFC running on ammonia weredescribed and its performance was compared with that when running on hydrogen.In order to improve the performance of the cell at higher temperatures, the anodewas modified by iron through infiltration. A direct comparison of the performance ofthe modified cell running on either hydrogen or ammonia showed that the cell inammonia generated slightly higher power densities at700and750oC. Theperformance in ammonia, using the anode catalyst, was comparable to that inhydrogen. The results indicated that ammonia could be treated as a promisingalternative fuel by selecting an appropriate catalyst.A novel doped CeO₂-LaFeO₃composite oxide as both the anode and cathode forsymmetrical solid oxide fuel cells was studied: A novel composite oxideCe（Mn,Fe）O2-La（Sr）Fe（Mn）O3（CFM-LSFM） was synthesized and evaluated as theelectrode material for a symmetrical solid oxide fuel cell. The symmetrical cell withCFM-LSFM electrodes was fabricated by tape-casting and screen printing technique.The power-generating performance of this cell was comparable to that of the cellwith the Ni-SSZ anode and LSM-SSZ cathode. During the120h long-term test inhydrogen at800oC, the performance increased by8.6%from256up to278mWcm-2. This was attributed to the decrease of polarization resistance and ohmicresistance during the test. The XRD results showed the presence of Fe, MnO andsome unknown second phases after heat-treating the electrode materials in H₂whichmay be beneficial to the anode process. The phenomenon of the gradual decrease of polarization resistance as the increase of current density possibly resulted from theincreasing content of water in the anode.更多还原