Composition and microstructure optimization and operation stability of barium deficient Ba_(1-x)Co_(0.7)Fe_(0.2)Nb_(0.1)O_(3-δ) perovskite oxide electrodes

摘要

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℃, 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 mWcm~(-2) at 650℃. 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℃. 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℃ for 400 h and maintained a reliable performance after repeated thermal cycles from room temperature to 700℃. 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.