SrCo0.8Nb0.1Ta0.1O3−δ Based Cathodes for Electrolyte-Supported Proton-Conducting Solid Oxide Fuel Cells: Comparison with Ba0.5Sr0.5Co0.8Fe0.2O3−δ Based Cathodes and Implications

Previous studies suggest that Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3− δ (BSCF) demonstrates high water uptake in humidified air and mixed protonic and electronic conduction as the cathode for intermediate temperature (∼400–600 o C) proton-conducting solid oxide fuel cells (PC-SOFC). However, whether such single phase mixed conducting cathodes would be optimal for the cathode oxygen reduction reaction (ORR) over PC-SOFC has not been well studied. In this research, another leading cathode material SrCo 0.8 Nb 0.1 Ta 0.1 O 3− δ (SCNT) is investigated and compared with BSCF as the cathode for BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3 (BZCYYb) electrolyte-supported PC-SOFC cells from 750 to 450 o C. The results show at intermediate temperature, pure SCNT displays negligible water uptake and lower performance than pure BSCF. On the other hand, SCNT-BZCYYb composite cathode perform better than both pure SCNT and pure BSCF, while BSCF-BZCYYb composite performs the worst. These observations suggest that the strong affinity to H 2 O for the single phase cathode of BSCF at intermediate temperature seems to inhibit oxygen adsorption and limits its performance as the cathode for PC-SOFC despite its mixed protonic and electronic conduction. In comparison, a composite cathode such as SCNT-BZCYYb might be more promising by enabling a better balance between the need for water absorption and proton conduction and the need for efficient oxygen adsorption/exchange.