钙钛矿基固体氧化物燃料电池电极材料结构及性能的研究

发布时间：2018-04-24 16:45

本文选题：固体氧化物燃料电池 + 钙钛矿　；参考：《北京科技大学》2016年博士论文

【摘要】：固体氧化物燃料电池(SOFCs)址一种将燃气中的化学能直接转化为电能的装置。凭借其清洁、高效、燃料适用性广以及全固态结构的特点,SOFCs被视为最具商业潜质的新型能源技术传统的Ni/YSZ阳极在使用碳氢燃料时会出现严重的碳沉积和硫中毒问题,导致电池性能严重衰减,因此需要开发新型高性能替代阳极材料。钙钛矿型阳极,在还原气氛下具有良好的结构稳定性,较强的抗积碳和硫中毒能力,是一类很有潜力的阳极替代材料。但该类材料存在催化活性差、离子电导率低、氧化还原结构稳定性差、电池性能不理想等问题。本论文围绕上述问题开展了系统研究。首先结合缺陷化学、材料晶体结构及元素特性,设计并合成了Sr2FeMo2/3Mg1/3O6-δ阳极材料,该材料具有优异的氧化还原结构稳定性、高的电导率、合适的热膨胀系数、高的氧表面交换系数以及优越的催化活性。由于Mg与Mo在离子电价和半径上存较大差异,Mg与Mo分别占据双钙钛矿结构中的B和B'位,导致过渡金属Fe同时占据双钙钛矿的B、B'位置,在材料晶格中形成高浓度的FeB-O-FeB键,因而该材料的实际晶体结构应为Sr2(Fe2/3Mg1/3)(Mo2/3Fe1/3)O6-δ。第一性原理计算结果表明材料中FeB-O-FeB键的形成有利于降低材料氧空位形成能以及迁移能,从而有效提高材料的氧离子电导率,改善材料的氧表面交换动力学过程,增强材料的电化学催化活性。以Sr2FeMo2/3Mg1/3O6-δ为阳极的电解质支撑型单电池在800,850和900℃时的最大功率分别为637,866和1044 mW cm-2,表明Sr2FeMo2/3Mg1/3O6-δ是一种非常有发展前途的SOFCs阳极候选材料。为进一步开发高性能阳极材料,我们首次将原位析出技术应用于双钙钛矿材料,设计并制备了Sr2FeMo0.65M0.3506 (M=Co, Ni)阳极材料。首先在空气中制备单相材料,然后在还原条件下实现Co-Fe、Ni-Fe纳米金属催化颗粒在该材料颗粒表面的原位析出,材料表层转变为RP相Sr3FeMoO7以及钙钛矿相SrFe1-XMoxO3,获得纳米金属颗粒修饰的钙钛矿阳极材料Sr2FeMo0.65Mo.3506 (M=Co, Ni)材料对H2和CH4表现出优异的电化学催化活性,以其为阳极的单电池功率在850℃纯H2中分别达到820和960mWcm-2;当以CH4为燃料时,电池功率分别达到430和500 mW cm-2。结果表明Sr2FeMo0.65Mo.3506 (M=Co, Ni)材料是一种非常有潜力的高性能SOFCs阳极材料。研究发现,上述双钙钛矿材料合成中极易出现的SrMoO4杂质,在阳极还原环境中可以转变成SrMoO3钙钛矿相,将之与电解质复合,制备的SrMoO3-60GDC复合阳极表现出良好的结构稳定性以及电化学催化活性。为建立结构与性能之间的关联性,本文从阳极材料Lao.3Sr0.7Ti03基体出发,通过在Ti位掺杂Co成功将其由阳极材料转变成一种结构稳定的高性能阴极材料Lao.3Sr0.7Ti1-xCoxO3-δ(x=0.3,0.45,0.6)。LSTC(x=0.45,0.6)材料具有高的电导率,优异的电化学催化活性以及与LSGM电解质具有优异的化学相容性。800℃时,LSTC(x=0.45,0.6)材料的极化电阻仅为0.0575和0.0233Ωcm2。通过实验与第一性原理计算相结合,揭示了LSTC材料电导性能、催化活性的演变原因。LSTC对氧还原反应的催化性能与其结构中的O 2p轨道中心具有良好的线性对应关系。通过第一性原理计算分析材料电子结构可预测材料催化活性的变化规律,从而实现高性能电极材料的理论设计。
[Abstract]:Solid oxide fuel cell (SOFCs) is a device for direct conversion of chemical energy in gas to electrical energy. By virtue of its cleaning, high efficiency, wide application of fuel and the characteristics of all solid state structures, SOFCs is regarded as the most commercial potential of new energy technology, the traditional Ni/YSZ anode will have serious carbon deposition in the use of hydrocarbon fuel. The problem of sulfur poisoning leads to the serious attenuation of battery performance, so a new type of high performance substitute anode material is needed. The perovskite type anode has good structural stability in the reduction atmosphere and strong ability to resist carbon and sulfur poisoning. It is a kind of potential anode substitute material. However, there are poor catalytic activity and ionic conductivity in this kind of material. Low stability of redox structure and poor battery performance. This paper has carried out a systematic study on the above problems. Firstly, the Sr2FeMo2/3Mg1/3O6- delta anode material was designed and synthesized by combining defect chemistry, crystal structure and element properties. The material has excellent stability of redox structure, high conductivity and suitable for this material. The thermal expansion coefficient, high oxygen surface exchange coefficient and superior catalytic activity. Due to the large difference between Mg and Mo in the ionic valence and radius, Mg and Mo occupy B and B'positions in the double perovskite structure respectively, causing the transition metal Fe to occupy the B of the double perovskite, B' position, and the high concentration FeB-O-FeB bond in the lattice of the material, so that the high concentration of the FeB-O-FeB bond is formed in the lattice. The actual crystal structure of the material should be Sr2 (Fe2/3Mg1/3) (Mo2/3Fe1/3) O6- Delta. The first principle calculation shows that the formation of FeB-O-FeB bond in the material is beneficial to reduce the formation energy of oxygen vacancy and the transfer energy, thus effectively improve the oxygen ion conductivity of the material, improve the oxygen surface exchange kinetics of the material, and enhance the electrification of the material. The maximum power of the electrolyte supported single cell with Sr2FeMo2/3Mg1/3O6- Delta as the anode is 637866 and 1044 mW cm-2 respectively at 800850 and 900 C, indicating that Sr2FeMo2/3Mg1/3O6- delta is a very promising candidate for the SOFCs anode. For the further development of high energy anode materials, we first precipitated in situ. The Sr2FeMo0.65M0.3506 (M=Co, Ni) anode materials were designed and prepared in the double perovskite materials. The single-phase materials were prepared in the air, and then Co-Fe was realized under the reduction conditions. The Ni-Fe nanoparticles were precipitated in situ on the surface of the material, and the surface of the material was transformed into RP phase Sr3FeMoO7 and perovskite SrFe1-XMox. O3, Sr2FeMo0.65Mo.3506 (M=Co, Ni) materials modified by nano metal particles showed excellent electrochemical catalytic activity for H2 and CH4. The single battery power of the anode was 820 and 960mWcm-2 in pure H2 at 850 degrees C. When CH4 was used as fuel, the battery power was 430 and 500 mW cm-2. showed Sr. The 2FeMo0.65Mo.3506 (M=Co, Ni) material is a highly potential high performance SOFCs anode material. It is found that the SrMoO4 impurity which is very easy to appear in the synthesis of the two perovskite materials can be transformed into the SrMoO3 perovskite phase in the anodic reduction environment, which is combined with the electrolyte, and the prepared SrMoO3-60GDC composite anode shows a good knot. Structure stability and electrochemical catalytic activity. In order to establish the relationship between structure and properties, this paper, starting from the anode material Lao.3Sr0.7Ti03 matrix, successfully transformed the anode material from the anode material into a stable high performance cathode material Lao.3Sr0.7Ti1-xCoxO3- Delta (x=0.3,0.45,0.6).LSTC (x=0.45,0.6) material by the Ti bit doping Co. High conductivity, excellent electrochemical catalytic activity and excellent chemical compatibility with LSGM electrolytes at.800 C, the polarization resistance of LSTC (x=0.45,0.6) material is only 0.0575 and 0.0233 Omega cm2. combined by experiment and first principle calculation, which reveals the conductivity of LSTC materials and the evolution of catalytic activity by.LSTC to oxygen reduction reaction. There is a good linear relationship between the catalytic properties and the O 2p orbit center in the structure. Through the first principle, the analysis of the change law of the catalytic activity of the material can be calculated and analyzed, thus the theoretical design of the high performance electrode material is realized.

【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O646.54;TM911.4

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