铜钴尖晶石基固体氧化物燃料电池阴极材料的制备及性能研究

发布时间：2018-02-27 04:22

本文关键词： 固体氧化物燃料电池阴极材料 CuCo_2O_4 复合阴极纳米阴极　出处：《哈尔滨工业大学》2017年博士论文　论文类型：学位论文

【摘要】：固体氧化物燃料电池(SOFC)是一种高效环保的电化学能源转换器件。中温化是目前国际SOFC领域的研究热点及发展趋势。然而,工作温度的降低会导致阴极材料催化活性的大幅度下降,成为制约中温SOFC发展的关键瓶颈之一。钴基钙钛矿材料具有良好的中温催化活性,但其与电解质的热、化学匹配性较差。本论文旨在提高阴极的中温反应活性,发展了一种新型、高性能电催化活性的SOFC阴极材料——尖晶石CuCo_2O_4,并对其物理化学性质、与电解质的相容性、电催化活性等进行了全面的表征。实验中进一步通过与高氧离子传导电解质复合构建了多种微结构的复合电极,深入研究探索了其反应机制、微结构与电化学性能之间的构效关系。通过溶胶凝胶法制备CuCo_2O_4纳米粉体。研究结果表明,当柠檬酸(CA)与乙二胺四乙酸(EDTA)的摩尔比增加至1:1.5时,可得到单相的立方晶相尖晶石CuCo_2O_4材料,材料晶粒尺寸小,约为70-200 nm,颗粒大小均匀。该材料与SSZ电解质具有较好的化学相容性,在50-900?C范围内的平均热膨胀系数11.76×10-6 K-1,与氧化钪稳定的氧化锆(SSZ)电解质热匹配性较好。在研究阴极烧结温度、造孔剂对CuCo_2O_4阴极微观形貌的影响规律基础上,得到最优的制备条件:阴极烧结温度为1000?C,淀粉添加25 wt.%。在800?C时,极化电阻为0.12W?cm2,单电池的最大功率密度972 m W?cm-2。为了提高CuCo_2O_4阴极的电催化反应活性,增加CuCo_2O_4阴极中的三相反应界面长度,研究中,在阴极中引入10 mol%Sc2O3稳定的Zr O2(SSZ)和Ce0.9Gd0.1O1.95(GDC)氧离子传导材料。采用机械混合法制备复合阴极,CuCo_2O_4-SSZ复合阴极和CuCo_2O_4-GDC复合阴极的平均热膨胀系数分别为11.39-11.86×10-6 K-1和11.83-12.20×10-6 K-1,与SOFC组件中其他组件热匹配性较好。电化学测试结果表明,随着复合阴极中氧离子电解质含量的增加,可有效地增加阴极中的三相反应界面长度,复合阴极化电阻减少,但含量过多时,会导致扩散电阻增加,导致极化电阻反而增大。其中,GDC的复合量为60 wt.%时,复合阴极的性能最佳,在800?C时,阴极的极化电阻为0.09W?cm2,当电流密度为0.5 A?cm-1时,CuCo_2O_4-GDC60复合阴极的阴极过电位为74 m V。单电池最大输出功率提高到1074m W?cm-2,展现出良好的稳定性。为了改善CuCo_2O_4阴极的性能,采用离子浸渍法原位制备CuCo_2O_4/SSZ纳米结构复合阴极。研究中考察了浸渍液的浓度、浸渍量及烧结温度对浸渍阴极微观结构的影响,得到浸渍液为0.025 mol/L时,浸渍CuCo_2O_4颗粒更均匀,浸渍4-5次,相对也较少。浸渍量为17.6 wt.%时,浸渍CuCo_2O_4效果较好。研究中发现烧结温度对浸渍CuCo_2O_4颗粒长大的影响不是很大,这可能是由于浸渍法制备材料过程中,热分解较低(360?C)。同时,SSZ多孔骨架有效地抑制了CuCo_2O_4的长大过程,保证了CuCo_2O_4没有出现粗化等现象。最终得到的纳米复合阴极结构稳定,SSZ多孔骨架有效地增加了三相反应界面区域和长度,提升CuCo_2O_4纳米阴极的氧化原催化活性,电化学性能得到明显提升,最佳浸渍量为17.6 wt.%的浸渍阴极具有最小的极化电阻,在800?C为0.08Ω?cm2,单电池最大输出功率为1136 m W?cm-2。同时,对浸渍CuCo_2O_4浸渍阴极的氧还原反应机制进行研究,得出氧离子在电极或从电极到电解质的三相反应界面的扩散过程是该电极反应的速率控制步骤。
[Abstract]:Solid oxide fuel cell (SOFC) is an efficient electrochemical energy conversion devices. The environmental temperature is research hotspot and development trend of the international SOFC field at present. However, lower working temperature will cause the cathode catalytic activity decreased greatly, become one of the key bottlenecks restricting the development of the temperature SOFC cobalt based perovskite. The temperature material has good catalytic activity, but the heat of the electrolyte, the chemical matching is poor. In this paper in order to improve the temperature and reaction activity of the cathode, the development of a new type of cathode, SOFC - spinel CuCo_2O_4 materials with high performance of electro catalytic activity, and the physical and chemical properties, compatibility with electrolyte. The electrocatalytic activity of the comprehensive experimental characterization. Further with high oxygen ion conducting electrolyte composite constructed composite electrodes with various microstructures, in-depth study and exploration of the reaction The mechanism and structure-activity relationship between microstructure and electrochemical properties. The preparation of CuCo_2O_4 nano powders by sol gel method. The results showed that when citric acid (CA) and EDTA (EDTA) molar ratio increased to 1:1.5, can get the single-phase cubic spinel CuCo_2O_4 material, material grain size is about 70-200. Nm, the particle size is uniform. The material with SSZ electrolyte has good chemical compatibility, in 50-900? The average thermal expansion coefficient of C within the range of 11.76 * 10-6 K-1, zirconium oxide and scandium oxide (SSZ) electrolyte heat stable matching is better. In the study of cathode sintering temperature, based on the CuCo_2O_4 cathode pore forming agent the influence of microstructure, the optimal preparation conditions are: cathode sintering temperature is 1000? C, starch adding 25 wt.%. at 800? C, the polarization resistance for 0.12W? Cm2, the maximum power density of 972 m W single cell cm-2. in order to improve the Cu? The electrocatalytic activity of Co_2O_4 cathode, increase of three-phase reaction interface length, CuCo_2O_4 cathode, introduced 10 mol%Sc2O3 stable Zr O2 in the cathode (SSZ) and Ce0.9Gd0.1O1.95 (GDC) oxygen ion conducting materials. The composite cathode with mechanical mixing method, CuCo_2O_4-SSZ composite cathode and the average thermal expansion coefficient of CuCo_2O_4-GDC composite cathode are 11.39-11.86 * 10-6 K-1 * 10-6 K-1 and 11.83-12.20, and other components of thermal SOFC components in good matching. The electrochemical test results show that with the increase of electrolyte content of composite cathode, can effectively increase the three-phase reaction interface length in the cathode polarization resistance, Yin composite decreased, but the content is too much, will to increase the resistance of diffusion, resulting in polarization resistance increases. The composite amount of GDC is 60 wt.%, the best performance of the composite cathode, at 800? C, cathodic polarization Resistance is 0.09W? Cm2, when the current density is 0.5 A? Cm-1, CuCo_2O_4-GDC60 composite cathode cathode overpotential is improved by 74 m V. single battery maximum power output to 1074m W? Cm-2, showing good stability. In order to improve the performance of CuCo_2O_4 cathode, by ion impregnation method for in situ preparation of nano CuCo_2O_4/SSZ composite cathode on the effects of the concentration of impregnation solution, impregnation impregnation amount and sintering temperature on the microstructure of the cathode by impregnating solution was 0.025 mol/L, dipping CuCo_2O_4 particles more evenly, dipping 4-5 times less. The dipping amount was 17.6 wt.%, the CuCo_2O_4 effect is not great. Good impregnation effect of sintering temperature to grow up on the impregnation of CuCo_2O_4 particles found in the study, this may be due to the material prepared by impregnation process, the thermal decomposition of low (360? C). At the same time, SSZ porous skeleton can efficiently inhibit the CuCo_2O_4 grown up The process, to ensure that the CuCo_2O_4 does not appear coarsening phenomenon. The nano composite cathode structure stable final, SSZ porous skeleton can effectively increase the three-phase reaction interface area and length, enhance the redox catalytic activity of CuCo_2O_4 nano cathode, electrochemical performance can be improved significantly, the best impregnation for impregnated cathode 17.6 wt.% with polarization resistance in 800, the minimum is 0.08 ohms? C? Cm2, the maximum output power of single cell was 1136 m W? Cm-2. CuCo_2O_4 at the same time, dipping on the impregnated cathode oxygen reduction reaction mechanism of the oxygen ion in the electrode or from the electrode to the diffusion process of three phase reaction interface electrolyte is the rate controlling step of the electrode reaction.

【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TM911.4

【相似文献】