管状固体氧化物燃料电池阳极支撑体的制备与电化学性能表征

1、管状固体氧化物燃料电池阳极支撑体的制备与电化学性能表征        【中文摘要】固体氧化物燃料电池(SOFC)是一种新型的发电装置,具有能量转换效率高、环境污染小、燃料的适应性强等优点,在当今全球能源短缺、能源供给形式相对单一以及环境污染日益严重的形势下被寄予厚看。随着SOFC技术的不断发展和完善,其贸易化进程不断推进。面对传统的SOFC在高温(1000°C左右)下运行所带来的材料技术和本钱方面的题目,以及氢气作为SOFC燃料的局限性,研究职员深刻地熟悉到降低电池的本钱和使用碳氢化合物作为燃料对于固体氧

2、化物燃料电池的贸易化具有重要意义。降低本钱可以通过开发新的电池制备技术和降低运行温度来实现。降低电池运行温度就需要进步电解质材料的电导率、降低电解质厚度和进步电极性能。通过电极结构的优化、修饰和开发新型电极材料,进而获得高催化活性和抗积碳的阳极,则是SOFC使用碳氢燃料的必要条件。鉴于此,本论文的出发点就是探索SOFC的低本钱制备技术,并且制备出单电池对其显微结构、输出性能和长期稳定性进行研究。另外,采用新技术制备出的管状阳极支撑体的孔隙率可以在大范围内进行调整,使后续的表面修饰成为可能。阳极经过修饰后的电池在通进氢气和甲烷时的稳定性测试和抗积炭题目得到进一步研究。论文的第一章简单先容了SOF

3、C的操纵原理,综述了SOFC各关键材料,重点讨论了SOFC的结构与制备和以碳氢燃料相关的阳极材料的最新研究进展。在概述了SOFC的发展现状和趋势的基础上,确立了本论文的研究目标和研究内容。关键材料的制备和电池*是SOFC技术的基础,对电极、电解质以及电池进行精确和有效的评价可以帮助我们选择合适的材料和综合评估SOFC的性能。因此第二章就本论文探索的制备工艺,烧结工艺和评价方法进行具体的先容,总的来讲分为电池阳极支撑体的制备和单电池的制作。管状阳极支撑体是采用注凝成型工艺(gel-casting)制备的Ni/YSZ金属陶瓷。在本论文中,我们利用注凝成型技术把陶瓷粉末和有机单体等制成低粘度高固相含

4、量的浓悬浮体,然后在温度和引发剂的作用下,使悬浮体中的有机单体交联聚合成三维网状结构,从而使悬浮体原位固化成型。近乎实现了净尺寸成型复杂外形的阳极支撑体,并且支撑体的强度足够,Ni和YSZ两相以及气孔分布均匀公道。具体研究了石墨作为造孔剂其添加量对支撑体的烧结收缩率和孔隙率的影响。单电池制作方法为阳极过渡层(dip-coating工艺)-电解质(dip-coating工艺)-阴极(涂覆工艺)。烧结工艺也是电池制备的关键。本论文采用的烧结工艺为阳极支撑体生坯预烧1150 oC-阳极及过渡层共烧1200 oC左右-阳极和电解质共烧1350 oC。表征方法有交流阻抗谱技术及激光粒度分布仪、扫描电子显

5、微技术(SEM)等。论文第三章先容了在以氢气为燃料气的情况下,阳极支撑体浸渍SDC对电池输出性能的影响。添加质量分数为15%的石墨使支撑体在还原前孔隙率接近30%,SDC的最佳浸渍量为273 mg/cm3,电池的极化阻抗降低了47%,最大输出功率密度进步了60%在700 oC时。电池分别在700 oC、750 oC和800 oC进行了I-V和I-P测试。电池的开路电压接近理论电压,并且浸渍的管状电池在800 oC时的最大输出功率密度达到了550 mW/cm2。电池在800 oC长期运行很稳定。电池测试过后的电镜图片表明电极与电解质接触良好,电解质很致密。另外,对浸渍的纳米级SDC颗粒在电池还原

6、和测试过程中的形貌变化进行了具体讨论。生物质能是一种洁净的可再生能源,它占居了世界总能源的13%。生物质气通过SOFC发电,能够进步能源转换效率,并降低污染物排放量,顺应了世界能源体系的发展方向。此时,开发高活性抗积碳阳极就成为关键技术题目之一。论文第四章先容了在以甲烷为燃料气的情况下,管状阳极支撑体浸渍SDC后的抗积炭性能。以SDC浸渍8次的电池为研究对象,对电池在直接通进甲烷作为燃料的稳定性能进行测试和氢气-甲烷不断切换下的循环性能进行测试。用SDC修饰的阳极在通进甲烷燃料气的情况下可以长期稳定的运行,而没有修饰的电池在24小时内性能衰减近50%。浸渍的SDC有效地抑制了积炭的发生。氢气和

7、甲烷循环测试表明燃料气的切换对电池的稳定性没有什么影响,但是在通进相同流量的燃料气时,通甲烷时的功率密度明显高于通氢气时的功率密度。');【Abstract】 Solid oxide fuel cell (SOFC) is a new energy conversion device which has been held the highest hopes because of their high efficiency, little pollution and flexibility in the choice of fuels, especially at the time w

8、hen the current energy structure is not reasonable and the environment pollution becomes more and more serious. As a new promising technique, it will fulfill the increasing need of electricity, improve the current energy structure, and impact the whole world environment actively in the near future.

9、With the development of SOFCs and its commercialization implementation, there are two main issues for SOFCs so far that are material technique and high cost problems related to high temperature operation ( 1000 oC) as well as the limit for hydrogen fuels with respect to efficiency, storage and trans

10、portation, etc. It is crucial, therefore, to reduce the cost and use hydrocarbon as the fuel for SOFCs. Looking for the efficient and cost-effective fabrication techniques and decreasing the thickness of electrolyte, developing novel electrolyte with higher ionic conductivity and new electrodes with

11、 higher performance are the major approaches to lower the cost. For direct utilization of hydrocarbon, it is necessary to fabricate the highly catalytic anode with the capability to avoid carbon deposition by modifying and optimizing the electrode microstructure or developing new materials.This thes

12、is aims to lower the cost and study the microstructure and electrochemicial performance of cells. In addition, the anode substrates prepared by the gel-casting technique have a large range of porosity, which make for the modification of the anode. The performance of the modified cell with hydrogen a

13、nd methane as fuels is studied.Chapter 1 reviews the working principle, materials for SOFC, especially main points of anode developments with methane as fuel. Proposal on the thesis work is also presented in this chapter.Preparation of key component materials and cells is basal technique in developi

14、ng SOFCs. Accurate and efficient characterization is critical in selecting suitable materials as well as overall evaluation of the performance of SOFC. Chapter 2 gives detail information about gel-casting technique, co-firing process and characterization technique. In our work, the ceramic powders a

15、nd organic materials were made into stable suspension with high solid loading. Monomers polymerized into three-dimensional structure and made the suspension into green body at 80 oC. The gelcasting process is more cost-effective and flexible for fabricating complex three-dimensional ceramic parts, a

16、nd also easy to scale up. The anode substrate which is uniform has enough strength. Effect of graphite addition on the porosity and sintering shrinkage of the substrate was studied. The single cell was fabricated by gel-casting, dip-coating and slurry-coating process. Firing process was 1150 oC(anod

17、e substrate)-1200 oC(anode substrate and interlayer)-1350 oC(anode and electrolyte co-firing). Characterization techniques are Ac impedance, laser granularity distributing analysis, scanning electron microscope (SEM) technique etc.In chapter 3, effect of SDC on the performance of cell with hydrogen

18、fuel was studied. Porosity of anode substrate before reduction was about 30% with 15% graphite addition, and the optimum SDC loading is 273 mg cm-3 after 6 repeat times of the impregnation cycle in our experiments. The peak power density of the cell was increased by about 60% and the area specific resistance (ASR) decreased by about 47% at 700 oC, compared with the unmodified cells. Performance of cell was tested at 700 oC, 750 oC and 800 oC. Results indicated that OCV(open current voltage) of cell reached nearly to the theory value. Electrode attached to the electrolyte well, and t