Composition and microstructure optimization and operation stability of barium deficient Ba_1-xCo_0.7Fe_0.2Nb _0.1O_3-δ perovskite oxide electrodes

Ba_1-xCo_0.7Fe_0.2Nb_0.1O _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_0.9Co_0.7Fe_0.2Nb_0.1O _3-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 Ba _0.9Co_0.7Fe_0.2Nb_0.1O _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_0.9Co_0.7Fe_0.2Nb_0.1O _3-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 Ba_0.9Co_0.7Fe _0.2Nb_0.1O_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_0.9Co_0.7Fe _0.2Nb_0.1O_3-δ was a promising cathode material for practical application in IT-SOFCs.