管式固体氧化物燃料电池的相转化制备与抗积碳研究

发布时间：2018-04-25 01:33

本文选题：固体氧化物燃料电池 + 相转化　；参考：《中国矿业大学(北京)》2017年博士论文

【摘要】：经济社会的快速发展对能源的需求不断增长,同时对环境的保护也更加重视。尽管近几十年来,水电、风电、太阳能等清洁能源发展迅速,但是目前世界能源供应仍以化石能源为主。为同时满足能源需求和环境保护,不仅要加快清洁可再生能源的发展,同时更要提高现有的化石能源的利用效率。固体氧化物燃料电池(Solid oxide fuel cell,SOFC)是一种在中高温下将蕴含在燃料气中化学能不经燃烧而直接转化为电能的能源转化技术,具有效率高、噪声低、燃料灵活等优点,具有很大的应用前景。尽管如此,关键材料和制备工艺的高成本限制了SOFC技术的推广应用。因此,在现有的可靠的材料体系基础上开展低成本的电池制备工艺研究很有必要。此外,尽管理论上SOFC对燃料气的要求比较灵活,可以使用质子交换膜燃料电池等无法使用的碳氢化合物为燃料,但是目前广泛使用的阳极材料在碳基燃料中的稳定性远远无法满足应用的要求。针对上述问题,本文以廉价的、目前最可靠的材料体系为基础,基于低成本、工艺简单的相转化法和共烧技术制备了多种管式SOFC,发展了新的电极优化工艺,探究了甲烷在阳极镍催化剂上的转化过程,为抗积碳研究提供了重要的理论基础。论文第三章发展了一种新的阳极改性方法——相转化浸渍法,在Ni-YSZ支撑管孔道内壁成功浸渍了纳米Fe、Ni和BaO,并研究了阳极改性对电池性能和稳定性的影响。与传统的相转化工艺不同,相转化浸渍法采用催化剂前驱体溶液为凝固浴。研究发现,采用相转化浸渍法制备NiO-YSZ阳极支撑管过程中,溶解在水中的催化剂前躯体可以在溶剂NMP和非溶剂水的相互扩散的驱动力下,分散到支撑体的各个部位,一步即可得到具有纳米催化剂的阳极支撑体。在800 oC下以湿氢为燃料时,浸渍Fe和浸渍Ni的Ni-YSZ阳极支撑管式SOFC的峰值功率密度分别提高到了0.40和0.48 W cm-2,以湿甲烷为燃料时峰值功率密度分别提高到了0.37和0.45 W cm-2。浸渍BaO的Ni-YSZ阳极支撑管式SOFC的峰值功率密度相对于未改性的电池性能有所下降,但甲烷下运行的稳定性大大提高,800 oC高温下运行100 h后电压仅衰减了0.17 V。本研究提出的相转化浸渍法相对于传统的浸渍法简化了工艺流程,提高了浸渍效率,具有很好的推广应用前景。论文第四章基于第一性原理计算研究了甲烷在SOFC阳极上与镍催化剂之间的相互作用及甲烷在镍催化剂上的转化过程。通过对比各个基元步骤的活化能,沿着含碳中间体的转化路径确定了甲烷转化过程的最低能量路径。在最低能量转化途径中,CH4首先通过CH4→CH3→CH2→CH→CHO→CO或CH4→CH3→CH2→CH→CHOH→CHO→CO两个路径转化为CO,然后再经过直接氧化CO→CO_2转化成CO_2。计算表明,甲烷的最低能量转化路径为中没有C的直接生成,积碳发生在表面含氧反应介质OH或O浓度低的区域。促进含氧介质扩散到甲烷和镍催化剂的两相界面(DPB)上,增加DPB界面上的含氧介质浓度,可以有效抑制积碳的产生。基于实验结果和理论分析,提出了碱土金属氧化物Ba O修饰Ni-YSZ阳极的抗积碳机理,认为BaO修饰提高了镍表面对H2O的捕获和解离能力,促进了Ni表面CH的消耗,避免了C的直接生成,从而抑制了积碳的产生。本研究的理论计算结果不仅合理解释了实验结果,同时为以后的抗积碳研究提供了理论基础。论文第五章采用相转化技术结合涂覆烧结工艺制备了多孔TZP陶瓷支撑管式SOFC,对其电化学性能进行了表征。为保证支撑管良好的透气性,添加了40 wt.%的球形石墨为造孔剂,1400 oC烧结后的支撑体的孔隙率达到40.15%,孔结构由非对称结构转变成对称结构。TZP陶瓷支撑管式SOFC单电池在800 oC氢气和甲烷燃料下,最大输出功率分别为0.25和0.20 W cm-2,氢气燃料下稳定运行100 h无明显衰减。电池表现出良好的氧化还原稳定性,经过8个氧化还原循环后,TZP陶瓷支撑管式SOFC的800 oC下的开路电压仍然可以达到1.02 V,峰值功率密度仍能达到0.26 W cm-2,继续恒流放电100 h后没有明显的性能衰减。以金属银为连接体成功制备了TZP陶瓷支撑多段串联管式SOFC(SIS-SOFC),以湿氢为燃料800 oC下两节和四节串联的电池开路电压分别达到了2.10 V和4.02 V,最大输出功率密度分别达到了0.24 W cm-2和0.22 W cm-2。基于TZP陶瓷支撑管式SOFC研究了阳极积碳后的消除方法,提出了通过电化学反应消除积碳的新策略,经过不同模式下35个CH4-H2循环后仍能恢复到初始的性能水平。论文第六章发展了新的金属支撑SOFC的制备工艺,以NiO和Fe2O3为原料,采用相转化法、涂覆烧结和原位还原的方法成功制备了Ni-Fe合金支撑管式SOFC,并对其电化学性能进行了表征。传统的金属支撑SOFC需要在还原气氛或者惰性气氛保护下制备,工艺繁琐,且对设备要求较高。本研究提出以金属氧化物为前驱体,在空气氛围下采用传统的共烧技术制备SOFC,然后测试前原位还原制得金属支撑SOFC。研究发现,NiO-Fe2O3支撑管坯体与NiO-YSZ阳极功能层、YSZ电解质在1400 oC下共烧有利于制备致密的YSZ电解质层。XRD分析表明,支撑管经原位还原后形成了Ni-Fe合金,既起到了支撑体的作用,又起到了阳极集电层的作用。在800 oC下,以湿氢气为燃料气时,Ni-Fe合金支撑管式SOFC的峰值输出达到0.26 W cm-2。相对于传统的金属支撑SOFC的制备方法,本研究提出的原位还原的方法大大简化了工艺难度,为金属支撑SOFC的制备提供了新思路。综上所述,低成本的相转化技术非常适合管式SOFC支撑体的制备,采用本论文提出的相转化浸渍法既可以浸渍活性催化剂用以提高电池的输出性能,还可以浸渍改性试剂用来改善电池的稳定性,有望应用于其他电化学器件的优化。SOFC阳极镍催化剂表面含氧介质的吸附和扩散对甲烷转化过程影响很大,及时地消耗CH中间体可显著抑制积碳的产生。积碳不仅可以通过燃烧除掉,还可以通过电化学反应消除掉。
[Abstract]:The rapid development of the economy and society has increased the demand for energy and more attention to the protection of the environment. Despite the rapid development of clean energy such as hydropower, wind power and solar energy in recent decades, the world's energy supply is still dominated by fossil energy. In order to meet energy demand and environmental protection at the same time, it is not only to speed up clean and renewable. Solid oxide fuel cell (SOFC) is a kind of energy conversion technology, which contains high efficiency, low noise, flexible fuel and so on. It has the advantages of high efficiency, low noise and flexible fuel. In spite of this, the high cost of key materials and preparation processes limited the promotion and application of SOFC technology. Therefore, it is necessary to carry out low cost battery preparation technology on the basis of the existing reliable material system. In addition, although the requirement for fuel gas is more flexible in theory, the proton exchange membrane can be used in SOFC. Fuel cells, such as fuel cells, can not be used as fuel, but the stability of the widely used anode materials in carbon based fuels is far from meeting the requirements of applications. This paper is based on cheap, most reliable material system based on low cost, simple process and CO combustion technology. A variety of tubular SOFC was prepared, and the new electrode optimization technology was developed. The conversion process of methane on the anode nickel catalyst was explored. The third chapter developed a new anodic modification method, phase transformation impregnation, and successfully impregnated the nano Fe, Ni and Ni on the inner wall of the channel of the support tube. BaO, and the effect of anodic modification on the performance and stability of the battery. Different from the traditional phase conversion process, the phase conversion impregnation method uses the catalyst precursor solution as the solidification bath. It is found that the precursor of the catalyst dissolved in the water can be dissolved in the solvent NMP and insoluble in the process of preparing the NiO-YSZ anode support tube by phase conversion impregnation. Under the driving force of the interdiffusion of water, the anode support with nanoscale catalyst can be obtained at all parts of the support. When the wet hydrogen is used as fuel at 800 oC, the peak power density of the Ni-YSZ anode supporting tube SOFC impregnated with Fe and Ni is increased to 0.40 and 0.48 W cm-2 respectively, and the peak of wet methane is the peak. The peak power density of the Ni-YSZ anode supporting tube SOFC of 0.37 and 0.45 W cm-2. impregnated BaO respectively is lower than that of the unmodified battery, but the stability of the operation under methane is greatly improved, and the voltage of 100 h at 800 oC at high temperature is only attenuated by the 0.17 V. proposed phase transformation impregnation method. The traditional impregnation method simplifies the process flow and improves the impregnation efficiency. The fourth chapter is based on the first principle to study the interaction between methane on the SOFC anode and the nickel catalyst and the process of methane conversion on the nickel catalyst. The lowest energy path of methane conversion process is determined by the conversion path of carbon containing intermediates. In the lowest energy conversion route, CH4 is first converted into two paths through CH4, CH3, CH2, CH, CHO, CO or CH4 to CH3 to CH2 to CH, CHOH, etc. The low energy conversion path is no direct generation of C, and carbon deposits occur in the area with low concentration of OH or O in the surface of oxygen containing reaction medium. Promoting the diffusion of oxygen medium to the two-phase interface (DPB) of methane and nickel catalyst, increasing the concentration of oxygen containing medium on the DPB interface, can effectively inhibit the production of carbon deposition. Based on experimental results and theoretical analysis, The anti carbon mechanism of the alkaline earth metal oxide Ba O modified Ni-YSZ anode has been developed. It is believed that BaO modification improves the capture and dissociation ability of the nickel surface to H2O, promotes the consumption of CH on the surface of the Ni, avoids the direct formation of C, and inhibits the production of carbon. The theoretical calculation of this study not only explained the experimental results reasonably, but also for the future. In the fifth chapter, a porous TZP ceramic support tube type SOFC was prepared by phase transformation and coating sintering, and its electrochemical performance was characterized. In order to ensure the good permeability of the support tube, the porosity of the support body after 1400 oC was added to the 40 wt.% spherical graphite as the pore forming agent. Up to 40.15%, the pore structure is transformed from asymmetrical structure to symmetrical structure, the.TZP ceramic support tube type SOFC single battery is under 800 oC hydrogen and methane fuel, the maximum output power is 0.25 and 0.20 W cm-2 respectively. The stable operation of 100 h under hydrogen fuel has no obvious attenuation. The battery shows good redox stability and passes through 8 redox cycles. After that, the open circuit voltage of the TZP ceramic support tube type SOFC under 800 oC can still reach 1.02 V, the peak power density can still reach 0.26 W cm-2. After continuing the constant current discharge 100 h, there is no obvious performance attenuation. The multi segment series SOFC (SIS-SOFC) of TZP ceramic support is prepared with the metal silver as the connecting body, and the wet hydrogen is used as the fuel 800 oC. The open circuit voltage of the battery in series with the four section reached 2.10 V and 4.02 V respectively. The maximum output power density reached 0.24 W cm-2 and 0.22 W cm-2., respectively, based on the TZP ceramic supporting tube SOFC to study the removal of the anode after carbon deposition. A new strategy to eliminate carbon deposition by electrochemical reaction was proposed, after 35 CH4-H2 cycles under different modes. In the sixth chapter, a new process for the preparation of a new metal supported SOFC is developed. Using NiO and Fe2O3 as raw materials, the Ni-Fe alloy support tube SOFC is successfully prepared by phase transformation, coating sintering and in situ reduction. The electrochemical properties of the SOFC are characterized. The traditional metal support SOFC needs to be in return. The preparation of the original atmosphere or inert atmosphere is tedious and requires high equipment. In this study, the metal oxide was used as the precursor and the traditional co firing technique was used in the air atmosphere to prepare SOFC, and then the metal support SOFC. was found in the former in situ reduction, and the NiO-Fe2O3 support tube body and the NiO-YSZ anode functional layer, YSZ The co firing of electrolytes at 1400 oC is beneficial to the preparation of compact YSZ electrolyte layer.XRD analysis, which indicates that the support tube has formed a Ni-Fe alloy after in situ reduction, which not only plays the role of the supporting body, but also plays the role of the anode collector layer. Under 800 oC, the peak output of the Ni-Fe alloy support tube SOFC reaches 0.26 W cm- when the wet hydrogen is used as fuel gas. 2. compared with the traditional method of preparing SOFC for metal support, the method of in situ reduction proposed in this study greatly simplifies the difficulty of the process and provides a new idea for the preparation of metal support SOFC. In summary, the low cost phase conversion technology is very suitable for the preparation of tubular SOFC support, and the phase transformation impregnation method proposed in this paper can not only be used in this paper. The impregnated active catalyst is used to improve the output performance of the battery, and the modified reagents can be impregnated to improve the stability of the battery. It is expected to be applied to the optimization of other electrochemical devices. The adsorption and diffusion of the oxygen containing medium on the surface of the.SOFC anode nickel catalyst has a great influence on the methane conversion process. The timely consumption of the intermediate of CH can significantly inhibit the carbon deposition. Carbon deposition can be removed not only by combustion, but also by electrochemical reaction.

【学位授予单位】：中国矿业大学(北京)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TM911.4

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