Improved thermal expansion and electrochemical performances of Ba0.6Sr0.4Co0.9Nb0.1O3−δ-Gd0.1Ce0.9O1.95 composite cathodes for IT-SOFCs

Ba0.6Sr0.4Co0.9Nb0.1O3−δ (BSCN)-xGd0.1Ce0.9O1.95 (GDC) composites with various GDC contents (x = 0-40, wt%) have been investigated for their potential application in IT-SOFCs. The effects of GDC addition on thermal expansion and electrochemical performances were studied. Thermal expansion measurement indicates that thermal expansion coefficients (TECs) decrease with increasing GDC content; in addition, GDC plays a catalytic role during the process of low-temperature thermal-driven reduction of Co4+ to Co3+. Polarization resistance (Rp) measurement indicates that the proper addition of GDC improves electrochemical performance of BSCN cathode. The optimum GDC addition to BSCN cathode is 20 wt% with the lowest Rp of 0.042 Ω cm2 at 700 °C. The maximum power density of a cell with BSCN-20GDC cathode on 300 μm-thick GDC electrolyte achieves 460-880 mW cm−2 at 700-800 °C. The excellent electrochemical performance of BSCN-20GDC composite cathode is ascribed to its much finer microstructure and larger cathode/electrolyte/gas triple phase boundary (TPB) areas.