Progress in understanding and development of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ-based cathodes for intermediate-temperature solid-oxide fuel cells: A review

Solid-oxide fuel cells (SOFCs) convert chemical energy directly into electric power in a highly efficient way. Lowering the operating temperature of SOFCs to around 500-800 °C is one of the main goals in current SOFC research. The associated benefits include reducing the difficulties associated with sealing and thermal degradation, allowing the use of low-cost metallic interconnectors and suppressing reactions between the cell components. However, the electrochemical activity of the cathode deteriorates dramatically with decreasing temperature for the typical La_0.8Sr_0.2MnO₃-based electrodes. The cathode becomes the limiting factor in determining the overall cell performance. Therefore, the development of new electrodes with high electrocatalytic activity for oxygen reduction becomes a critical issue for intermediate-temperature (IT)-SOFCs. Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ (BSCF) perovskite oxide was first reported as a potential IT-SOFC cathode material in 2004 by Shao and Haile. After that, the BSCF cathode has attracted considerable attention. This paper reviews the current research activities on BSCF-based cathodes for IT-SOFCs. Emphasis will be placed on the understanding and optimization of BSCF-based materials. The issues raised by the BSCF cathode are also presented and analyzed to provide some guidelines in the search for the new generation of cathode materials for IT-SOFCs.