ZHOU Lihong ¹, XIONG Xiaosong ¹, JI Ninglin ¹, ZHANG Ding ¹, XIAO Jianzhong ²

(1. City College, Wuhan University of Science and Technology, Wuhan 430083, Hubei, China; 2. School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, Hubei, China)

Abstract: Layered perovskite oxide YBaCo₂O_5+δ (YBC), as cathode material of intermediate-temperature solid oxide fuel cell, was modified by doping and coating to improve its electrochemical performance. The YBC and YBa_0.5Sr_0.5Co₂O_5+δ (YBSC) oxide powders were synthesized by using an ethylenediaminetetraacetic acid-citric acid complex method. La₂NiO_4+δ (LN) coated YBSC composite cathode, designated as La₂NiO_4+δ@YBa_0.5Sr_0.5Co₂O_5+δ (LN-YBSC), was prepared by using a solution dipping method. Properties of the materials, such as phases and conductivities of the powders, microscopic morphologies and electrochemical performances of the cathodes, were investigated. It was demonstrated that LN is single-phase with Ruddlesden-Popper structure. The Sr-doped YBSC still has a tetragonal crystal structure, which is consistent with the YBC structure. The increasing interstitial oxygen concentration after Sr doping resulted in an increase in the concentration of holes, which is responsible for the high electronic conductivity of the materials. LN is closely and continuously distributed on surface of the YBSC framework, thus forming a coating structure. Compared with the YBSC cathode, the LN-YBSC cathode had lower polarization impedance. The electrochemical performance of the YBSC was improved after the coating of LN, due mainly to the enhanced oxygen surface exchange performance of the LN.

Key words: double perovskite; coated; composite cathode; intermedium-temperature solid oxide fuel cell