中低温固体氧化物燃料电池Ce_(0.9)Gd_(0.1)O_(2-δ)纤维骨架复合阴极的构建与电化学性能研究

Construction and Electrochemical Performance of Ce_(0.9)Gd_(0.1)O_(2-δ) Fiber Skeleton Composite Cathode for Medium and Low Temperature Solid Oxide Fuel Cells

为了降低固体氧化物燃料电池(Solid Oxide of Fuel Cell, SOFC)的操作温度,需要将SOFC的阴极催化活性提高,为此,设计和构建了一种SOFC的Ce_(0.9)Gd_(0.1)O_(2-δ)(GDC)纤维骨架复合阴极,最终获得了较低的阴极阻抗。采用溶胶—凝胶法结合静电纺丝制备GDC纤维前驱体,在950℃下煅烧得到一维纳米纤维棒,再与GDC电解质在1450℃下共烧得到孔隙率为70 vol.%孔隙率的纤维骨架。分别采用浸渍LSCF离子溶液和LSCF粉体悬浮液制备出纤维骨架复合阴极,并与传统的LSCF-GDC粉体阴极进行微观结构和电化学性能对比,结果表明制备的纤维骨架复合阴极具有较多的三相界面处,两种骨架阴极的极化阻抗均小于传统阴极极化阻抗。采用弛豫时间分布法分析三种对称电池的极化阻抗,明确了在GDC纤维骨架上浸渍LSCF离子溶液明显提高阴极性能的原因。构造的纤维骨架复合阴极可以克服传统阴极与电解质界面结合活性较差或因晶粒长大导致的阴极三相界面变少的问题,且在550℃~750℃的各个测试温度点,其极化阻抗值均低于传统阴极极化阻抗值约一个数量级,在650℃极化电阻仅为0.050Ω·cm^(2),小于传统复合阴极650℃下的极化阻抗0.280Ω·cm^(2)。因此本研究所获得的阴极是一种可在中低温下使用的SOFC高催化活性纤维骨架复合阴极。

In order to reduce the operating temperature of solid oxide fuel cell(SOFC),it is necessary to increase the catalytic activity of the cathode.In this study,a GDC fiber skeleton composite cathode for SOFC was designed and constructed,with relatively low cathode impedance.The GDC fiber precursor was prepared by using a sol-gel method combined with electrospinning.The nanofiber rods were calcined at 950℃,forming fiber skeleton with a porosity of 70 vol.%,which was co-sintered with GDC electrolyte at 1450℃.The composite cathode of fiber skeleton was prepared with macerated LSCF ion solution and LSCF powder suspension.Microstructure and electrochemical properties were compared with those of the traditional LSCF-GDC powder cathode.It is found that the fiber skeleton composite cathode has rich three-phase interfaces,while the polarization impedance of the two skeleton cathode is less than that of the traditional cathode.The polarization impedance of three symmetric cells was analyzed by using the relaxation time distribution method.The reason why the performance of the cathode could be significantly improved by impregnating LSCF ion solution on the GDC fiber skeleton was identified.With the fiber skeleton composite cathode,the problem of poor bonding activity between the traditional cathode and electrolyte interface was overcome and the three-phase cathode interface was reduced due to grain growth.Specifically,the polarization impedance is about one order of magnitude lower than that of the traditional cathode at each test temperature over 550-750 C.At 650℃,the polarization resistance is only 0.05 Ω·cm^(2),which is slightly lower than that of 0.280 Ω·cm^(2)at 650℃ for conventional composite cathode.Therefore,the fiber skeleton composite cathode obtained in this study has high catalytic activity,making it suitable for medium and low temperature applications.