【作者】 张雷；

【导师】 李小武；

【作者基本信息】 东北大学 ， 材料物理与化学， 2019， 博士

【摘要】 传统的固体氧化燃料电池(SOFC)需要在1000℃左右工作,较高的工作温度严重影响了其商业化进程,而单纯的降低操作温度又会影响SOFC的输出性能。作为SOFC的重要组成部件,阴极材料性能的好坏会直接影响到SOFC的输出性能。因此,开发具有高性能输出的中温(600～850℃)固体氧化物燃料电池(IT-SOFC)阴极材料是该领域的研究重点。本论文主要制备了 LaxSr1-xCo0.9Sb0.1O3-δ、La0.4Sr0.6Co0.9Sb0.1O3-δ-xCe0.8Sm0.2O1.9 和BaxSr1-xCo0.9Sb0.1O3-δ三类新型钴基钙钛矿阴极材料,并对其物理及化学性能进行了系统测试,研究了稀土离子(La3+)和碱土离子(Ba2+)掺杂以及复合电解质对阴极性能的影响,并对物理和化学性能变化的原因进行了系统分析,论证其作为IT-SOFC阴极材料的可行性。利用固相反应法制备了LaxSr1-xCo0.9Sb0.1O3-δ(LSCSbx,x=0.0～0.8)阴极材料。1200℃烧结10 h的LSCSbx样品具有稳定的四方钙钛矿结构,空间群类型为P4/mmm,LSCSb0.6 和 LSCSb0.8 样品中出现了杂质相 La2Co205,LSCSbx(x=0.0～0.6)样品的晶胞体积随La元素含量的增加逐渐减小。经1050℃煅烧6 h后,LSCSb0.2和LSCSb0.4样品分别与La0.9Sr0.1Ga0.8Mg0.2O3-δ(LSGM)电解质之间保持良好的化学兼容性。X射线光电子能谱(XPS)实验结果表明,LSCSbx(x=0.0～0.4)样品中Co3+与Co4+含量比随La掺杂而增大。电导率测试表明,LSCSbx(x=0.0～0.4)的电导率随La含量的增加逐渐增大,LSCSb0.4样品在300～850℃范围内的电导率高达673～1637 S cm-1。LSCSbx(x=0.0～0.6)样品的热膨胀系数(TEC)随La元素含量的增加逐渐降低,LSCSb0.6 样品在 30～900℃ 范围内的 TEC 为 18.50 × 10-6 K-1。700℃ 时,LSCSb0.2 样品在LSGM电解质上的极化阻抗最低,仅为0.069 Ω cm2。以0.3 mm厚LSGM为电解质,以NiO-SDC为阳极,并以SDC为缓冲层制备单电池,LSCSb0.2样品的电池性能最好,而且在700℃连续运行20 h性能几乎无衰减。利用物理复合的方法制备了 La0.4Sr0.6Co0.9Sb0.1O3-δ-xCe0.8Sm0.2O1.9(LSCSb-xSDC,x=0,20,30,40,50wt.%)复合阴极材料。1050℃ 煅烧 10h 后,LSCSb0.4 与 SDC 保持良好的化学兼容性。LSCSb-xSDC(x=0～50)样品的电导率随SDC含量的增加而逐渐下降,但均大于100 S cm-1。LSCSb-xSDC(x=0～50)样品的TEC随SDC含量的增加逐渐降低,30～900℃范围内LSCSb-50SDC的TEC仅为13.1 × 10-6 K-1。LSCSb-xSDC(x=0～50)样品在LSGM电解质上的极化阻抗随SDC含量的增加逐渐降低,700℃时,LSCSb-50SDC样品的极化阻抗(Rp)为0.086 Ωcm2。采用与之前相同方法制备单电池,LSCSb-xSDC样品电池性能逐渐升高,850℃时,LSCSb-50SDC样品功率密度高达793 mW cm-2,而且在700℃连续运行20 h性能无衰减。SEM实验结果表明,SDC的引入增加了三相反应界面(TPB)的长度,扩展了电化学反应活性区域,这有利于提高复合阴极材料的电催化活性。利用固相反应法制备了 BaxSr1-xCo0.9Sb0.1O3-δ(BSCSbx,x=0.0～0.8)阴极材料。x=0.0～0.4样品经1050℃烧结10h,x=0.6～0.8样品经1100℃烧结10h,烧结后的样品均呈现稳定的四方钙钛矿结构,晶胞体积随Ba元素含量的增加逐渐增大。XRD结构精修结果表明,样品空间群类型为P4/mmm。经1000℃煅烧6 h后,BSCSb0.2和BSCSb0.4分别与LSGM保持良好的高温化学相容性。XPS实验结果表明,BSCSbx(x=0.0～0.8)样品中Co3+与Co4+的含量比随Ba元素含量的增加逐渐增大。碘滴定和热重(TGA)实验表明,Ba2+的引入有利于高温下氧空位浓度的增大。BSCSbx的电导率随Ba含量的增加而有所下降。BSCSbx(x=0.0～0.6)的TEC随Ba元素含量的增加逐渐降低,30～1000℃ 范围 BSCSb0.6 的 TEC 为 18.4 × 10-6 K-1。BSCSbx(x=0.0～0.6)样品在 LSGM电解质上的极化阻抗随Ba元素含量的增加逐渐降低。700℃时,BSCSb0.6样品的极化阻抗仅为0.082Ωcm2。采用相同方法制备单电池,电池性能随阴极体系中Ba含量的增加逐渐升高,850℃时,BSCSb0.6样品功率密度高达944 mW cm-2,而且在700℃连续运行20 h电池性能几乎无衰减。更多还原

【Abstract】 The operation temperature of traditional solid oxide fuel cell(SOFC)is～1000℃,and the higher operation temperature hinders its commercialization;however,the performance of SOFC will be greatly reduced when the operating temperature is decreased.Cathode is an important component of SOFC,which will directly affect the output performance of SOFC.Therefore,it is necessary to develop novel cathode materials with high performance for solid oxide fuel cell(IT-SOFC)running at intermediate temperatures(600～850℃).In this paper,three kinds of novel cobalt-based perovskite cathode materials LaxSr1-xCo0.9Sb0.103-δ,La0.4Sr0.6Co0.9Sb0.1O3-δ-xCe0.8Sm0.2O1.9 and BaxSr1-xCo0.9Sb0.1O3-δwere prepared and the physical and chemical performances were studied systematically.The effects of La/Ba doping or electrolyte introduction on the performance of SrCoO3-based cathode were analyzed,and the feasibility of these materials used as cathodes of IT-SOFCs was assessed.Cobalt-based perovskite cathode materials LaxSr1-xCo0.9Sb0.103-δ(LSCSbx,x=0.0～0.8)were prepared via a solid-state reaction method.The LSCSbx samples sintered at 1200℃ for 10 h have a tetragonal structure with space group P4/mmm,however,an impurity phase of La2Co2O5 was observed in the samples with x=0.6 and x=0.8,and the unit-cell volumes decrease with the doping level from x=0.0 to x=0.6.The LSCSb0.2 and LSCSb0.4 samples have a good chemical compatibility with LSGM after calcined at 1050℃ for 6 h,respectively.X-ray photoelectron spectroscopy(XPS)examinations indicate that the molar ratio of Co3+to Co4+increases gradually in LSCSbx samples from x=0.0 to x=0.4.The electrical conductivity increases with the doping level from x=0.0 to x=0.4 and the highest electrical conductivity of LSCSb0.4 sample is 673～1637 S cm-1 in the temperature range of 300～850℃.The thermal expansion coefficients(TECs)decrease with the doping level and the minimum TEC is 18.50 × 10-6 K-1 for the LSCSb0.6 samples in the temperature range of 30～900℃.The lowest polarization resistance(Rp)for the LSCSb0.2 sample on LSGM electrolyte is merely 0.069 Ω cm2 at 700℃.The single cells were prepared using 0.3 mm thick LSGM as electrolyte,NiO-SDC as anode and SDC as buffer layer,the LSCSb0.2 sample possesses the best cell performance,and there is almost no attenuation of performance after a 20 h testing at 700℃.Composite cathode materials La0.4Sr0.6Co0.9Sb0.1O3-δ-xCe0.8Sm0.2O1.9(LSCSb-xSDC,x=0,20,30,40,50 wt.%)were prepared via a physical composite method.The LSCSb0.4 samples have a good chemical compatibility with SDC after calcined at 1050℃ for 6 h.The electrical conductivity decreases with the increase of SDC content,but all the experimental results are still beyond 100 S cm-1 at 300～850℃.The TECs of LSCSb-xSDC are reduced with increasing SDC content and the lowest TEC for the LSCSb-50SDC sample is 13.1 ×10-6 K-1 in the temperature range of 30～900℃.The Rp decreases with the SDC content from x=0.0 to x=50 on the LSGM electrolyte,and the lowest Rp of LSCSb-50SDC sample is 0.086 Ωcm2 at 700℃.The single cells were prepared by the same way above,the maximum power density of LSCSb-50SDC sample is 793 mW cm-2 at 850℃,and there is almost no attenuation of performance after a 20 h testing at 700℃.Scanning electron microscopy(SEM)observations show that the introduction of SDC can enlarge the length of TPB and expand the active region of electrochemical reaction,which can improve the electrocatalytic activity of composite cathodes.Cobalt-based perovskite cathode materials BaxSr1-xCo0.95b0.1O3-δ(BSCSbx,x=0.0-0.8)were prepared via a solid-state reaction method.The BSCSbx samples with x=0.0～0.4 sintered at 1050℃ for 10 h and with x=0.6～0.8 sintered at 1100℃ for 10 h are crystallized in a tetragonal structure,and the unit-cell volumes increase with the doping level.X-ray diffraction(XRD)refinement shows that all the samples have space group with P4/mmm.The BSCSb0.4 and BSCSb0.6 samples have a good chemical compatibility with LSGM electrolyte after calcined at 1050℃ for 6 h,respectively.XPS examinations show that the molar ratio of Co3+to Co4+increases gradually.The iodometric titration method and thermogravimetric analysis(TGA)experiments indicate that the oxygen vacancy concentration will increase with increasing content of Ba2+.The electrical conductivity decreases with the doping level.The TECs decrease with the doping level from x=0.0 to x=0.6 and the minimum TEC is 18.50 ×10-6 K-1 for the BSCSb0.6 samples in the temperature range of 30～1000℃.The Rp decreases from x=0.0 to x=0.6 on the LSGM electrolyte,and the lowest Rp of BSCSb0.6 sample is 0.082 Ω cm2 at 700℃.The single cells were prepared by the same way above,the maximum power density increases from x=0.0 to x=0.6 and for the x=0.6 cathode,and the maximum power density of 944 mW cm-2 was attained at 850℃.Furthermore,almost no attenuation of performance was observed after 20 h testing at 700℃.更多还原