XIONG Bin ¹, CHENG Liang ^{1, 2}, LUO Linghong ^{1, 3}, LIU Shaoshuai ^{1, 3}, WANG Leying ^{1, 3}, XU Xu ^{1, 3}
(1. School of Materials Science and Engineering, Jingdezhen Ceramic University, Jingdezhen 333403, Jiangxi, China; 2. National Engineering Research Center for Domestic & Building Ceramics Jingdezhen Ceramic University, Jingdezhen 333001, Jiangxi, China; 3. Jiangxi Provincial Key Laboratory of Fuel Cell Materials and Devices, Jingdezhen Ceramic University, Jingdezhen 333001, Jiangxi, China)

Abstract: 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℃. At 650℃, the polarization resistance is only 0.05 ·cm², which is slightly lower than that of 0.280·cm² 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.
Key words: intermediate low temperature solid oxide fuel cell; composite cathode; fiber skeleton; electrochemical impedance spectroscopy