Composition and microstructure optimization and operation stability of barium deficient Ba1−xCo0.7Fe0.2Nb0.1O3−δ perovskite oxide electrodes

Ba 1− x Co 0.7 Fe 0.2 Nb 0.1 O 3− δ oxides ( x   =   0, 0.05 and 0.10) were optimized as potential cathodes on oxygen ionic conductor electrolyte for intermediate temperature solid oxide fuel cells (IT-SOFCs). The creation of additional oxygen vacancies in Ba 0.9 Co 0.7 Fe 0.2 Nb 0.1 O 3− δ was confirmed. Low polarization resistances of 0.015, 0.029 and 0.089   Ω   cm 2 were achieved at 700, 650 and 600   °C, respectively. By further optimizing the microstructure of the Ba 0.9 Co 0.7 Fe 0.2 Nb 0.1 O 3− δ electrode by using polyvinyl butyral as a pore former and adjusting the sintering temperature, the maximum power density was improved from 682 to 955   mW   cm −2 at 650   °C. The operational stability of the Ba 0.9 Co 0.7 Fe 0.2 Nb 0.1 O 3− δ electrode was also investigated. The CO 2 in the surrounding air was detrimental to the oxygen reduction reaction ; however, the performance of the cell was recovered after removing the CO 2 in the air at 650 or 700   °C. In addition, the Ba 0.9 Co 0.7 Fe 0.2 Nb 0.1 O 3− δ electrode in symmetrical cells exhibited a stable performance at 650   °C for 400   h and maintained a reliable performance after repeated thermal cycles from room temperature to 700   °C. The results showed that Ba 0.9 Co 0.7 Fe 0.2 Nb 0.1 O 3− δ was a promising cathode material for practical application in IT-SOFCs.