Development of a new ceria/yttria-ceria double-doped bismuth oxide bilayer electrolyte low-temperature SOFC with higher stability

Abstract

A new anode-supported ceria/bismuth oxide bilayer electrolyte solid oxide fuel cell (SOFC) was developed. Yittria-ceria double-doped bismuth oxide (Bi0.75Y0.25)1.86Ce0.14O3\u2009±\u2009δ, (YCSB) which showed stable ionic conductivity across the temperature range of 650–500\xa0°C was used as both the second electrolyte layer and as the oxygen ion conductor phase in the cathode. For a cell with a ~\u200920\xa0μm 10% gadolinium-doped ceria (GDC) layer and a ~\u200912–13\xa0μm YCSB layer, open circuit voltage (OCV) and maximum power density (MPD) of the cell at 650\xa0°C reached 0.833\xa0V and 760\xa0mW/cm2, respectively. OCV stability of this bilayer was measured for 50\xa0h at 625 and 600\xa0°C (100\xa0h in total), and exceptional stability of OCV with zero degradation was observed. In comparison, the cell with 10GDC/erbium-stabilized bismuth oxide (ESB) bilayer electrolyte showed a very rapid degradation of OCV at 600\xa0°C (average hourly degradation rate of −\u20090.55%/h). In addition to the exceptional OCV stability, this new bilayer electrolyte exhibited no ohmic area-specific resistance (ASR) degradation at 600 and 625\xa0°C. In contrast, the ohmic ASR of the cell with 10GDC/ESB bilayer electrolyte at 600\xa0°C increased by five times over the first 50\xa0h of operation mainly due to the conductivity decay of ESB. The rate of non-ohmic ASR degradation was also decreased by replacing the ESB with YCSB in the cathode structure.