Effects of La0.8Sr0.2MnO3 and Ag electrodes on bismuth-oxide-based low-temperature solid electrolyte oxygen generators

Abstract

In this study, La 0.8 Sr 0.2 MnO 3 (LSM) was used as the ceramic electrode in a (Bi 1.50 Y 0.50 ) 0.98 Zr 0.04 O 3+δ (BYO)-based solid electrolyte oxygen generator (SEOG) and its performance was compared with that of a previously studied high-fire Ag electrode. Among La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 , LaNi 0.6 Fe 0.4 O 3 , Cu 1.4 Mn 1.6 O 4 , and LSM materials, only LSM materials did not trigger any chemical reaction or interdiffusion with BYO at temperatures up to 900 °C. Two cell designs, Cell A, with a Bi 1.71 Nb 0.25 Ba 0.04 O 3+δ (BBNO) interlayer and high-fire Ag electrode, and Cell B, with an LSM-BYO composite electrode, were obtained in this study. The cells were sandwiched between two modular SUS 316 planar interconnects using a ZnO–SiO 2 –Al 2 O 3 glass sealant to form the SEOG device. Although Cells A and B possessed similar ohmic resistance (R o ) values, the polarization resistance (R p ) values of Cell A were 3.6 times larger than those of Cell B. Furthermore, the stability study of the cells operated at 600 °C for 12 h revealed that R o increased from 0.79 to 3.17 Ω cm 2 and R p from 3.12 to 12.58 Ω cm 2 for the Cell A, while R o increased from 0.76 to 0.77 Ω cm 2 and R p from 0.87 to 1.12 Ω cm 2 for the Cell B. Therefore, minor variations in the R o and R p of Cell B indicate the excellent stability of the electrode. The degradation of Cell A was caused by the migration of Ag and formation of voids and cracks adjacent to the anode/electrolyte interface under the DC field. Furthermore, the Cell A experienced a decrease in faradaic efficiency for current densities greater than 0.20 A cm −2 owing to the partial decomposition of BYO at the cathode. In contrast, the Cell B generated an oxygen flux of 1.29 cm⋅min −1 at 600 °C. In addition, the faradaic efficiency of Cell B remained consistent for current densities up to 0.35 A cm −2 . Therefore, the SEOG using LSM-BYO as the cell electrode exhibited excellent stability and electrochemical performance.