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 Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) demonstrates high water uptake in humidified air and mixed protonic and electronic conduction as the cathode for intermediate temperature (∼400-600 oC) 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 SrCo0.8Nb0.1Ta0.1O3−δ (SCNT) is investigated and compared with BSCF as the cathode for BaZr0.1Ce0.7Y0.1Yb0.1O3 (BZCYYb) electrolyte-supported PC-SOFC cells from 750 to 450 oC. 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 H2O 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.