中温固体氧化物燃料电池复合阴极材料LaBiMn_2O_6-Sm_(0.2)Ce_(0.8)O_(1.9)的制备与电化学性质

Preparation and Electrochemical Properties of LaBiMn_2O_6-Sm_(0.2)Ce_(0.8)O_(1.9)Composite Cathode for IT-SOFCs

采用甘氨酸燃烧法合成了LaBiMn_2O_6粉体,并与Sm_(0.2)Ce_(0.8)O_(1.9)均匀混合制备了LaBiMn_2O_6-Sm_(0.2)Ce_(0.8)O_(1.9)(LBM-SDC)复合阴极材料。利用X射线衍射(XRD)和扫描电子显微镜(SEM)对材料的物相及微观形貌进行分析,结果表明LBM与SDC在1 000℃下有良好的化学稳定性。SDC的复合增加了氧离子传导路径,进而使氧还原反应(ORR)速度加快。电化学阻抗谱(EIS)测试结果表明,复合阴极极化电阻(Rp)随SDC复合量的增加呈现先降低后升高的趋势,当复合量为30%(w/w)时,阴极材料的性能最优。在700℃空气气氛下的极化电阻为0.186Ω·cm^2,相对LBM(0.717Ω·cm^2)减少74%。氧分压测试结果表明阴极反应的速率控制步骤为氧分子的吸附-解离过程。以复合阴极构筑的电解质支撑单电池Ni-SDC/SDC/LBM-30%SDC在700℃的最大输出功率密度为234 mW·cm^(-2),连续测试90 h输出功率衰减约4%。

The composite cathode LaBiMn2O6-Sm0.2Ce0.8O1.9(LBM-SDC)was prepared by glycine-nitrate combustion method.The phase and morphology evolution of the composite cathode were characterized by X-ray diffraction(XRD)and scanning electron microscopy(SEM),respectively.The results showed that LBM had good chemical stability with SDC at 1 000℃.Due to the introduction of SDC,the length of the thriple-phase boundary was extended and the thermal matching between the cathode and the electrolyte was enhanced,resulting in an improvement in the electrochemical performance of the composite cathode.The electrochemical impedance spectrum(EIS)results indicated that the cathode polarization resistance(Rp)decreased steadily with the addition of SDC.The optimum addition of 30%(w/w)SDC in the composite cathode leads to the lowest Rpof 0.186Ω·cm2 at 700℃in air,which is 74%less than the pristine LBM cathode(RP=0.717Ω·cm2).This is because an additional oxygen ion conduction path is generated after the introduction of SDC;thereby the oxygen reduction reaction is promoted.The maximum power density of the electrolyte-support single cell Ni-SDC/SDC/LBM-30%SDC reached 234 mW·cm-2 at 700℃.The power density maintains a stable value at 230 mW·cm-2 throughout a test period of 90 h,indicating that LBM-30%SDC had sufficient stability during the operation.The oxygen partial pressure measurement indicated that the oxygen molecule adsorption-diffusion process is the reaction rate-limiting step of the composite cathode.