Synthesis, structure and electrochemical performance of cobaltite-based composite cathodes for IT-SOFC

摘要

The development of novel and high-performance cathodes is a critical issue to be addressed in order to reduce Solid Oxide Fuel Cells (SOFCs) operation temperature to the 600-800 ℃ range or less. The performance of CeO_2-based composite cathodes is very attractive to such operational temperatures. In this work, La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_3 (LSCF) and Ce_(0.8)Sm_(0.2)O_(1.9) (SDC) powders were synthesized by different synthesis methods and mechanically mixed to prepare LSCF-SDC composite cathodes. Screen-printed LSCFSDC/ CGO/LSCF-SDC symmetrical cells were sintered at 1150 ℃ for 4 h and characterized by electrochemical impedance spectroscopy in static air. X-ray diffraction and scanning electron microscopy were employed to characterize the powders. Area specific resistance values of 0.72 and 2.77 ? cm~2 at 800 ℃ were found for composite cathodes containing SDC powder synthesized by modified Pechini and microwave-assisted combustion methods, respectively. Furthermore, the activation energy of the composite cathode containing SDC derived from modified Pechini method is 1.18 eV, i.e., much lower than 1.73 eV, value determined for LSCF with SDC from microwave-combustion method.