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

Ba1−xCo0.7Fe0.2Nb0.1O3−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 Ba0.9Co0.7Fe0.2Nb0.1O3−δ was confirmed. Low polarization resistances of 0.015, 0.029 and 0.089 Ω cm2 were achieved at 700, 650 and 600 °C, respectively. By further optimizing the microstructure of the Ba0.9Co0.7Fe0.2Nb0.1O3−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 Ba0.9Co0.7Fe0.2Nb0.1O3−δ electrode was also investigated. The CO2 in the surrounding air was detrimental to the oxygen reduction reaction; however, the performance of the cell was recovered after removing the CO2 in the air at 650 or 700 °C. In addition, the Ba0.9Co0.7Fe0.2Nb0.1O3−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 Ba0.9Co0.7Fe0.2Nb0.1O3−δ was a promising cathode material for practical application in IT-SOFCs.