Effects of (LaSr)(CoFeCu)O_(3-δ) cathodes on the characteristics of intermediate temperature solid oxide fuel cells

摘要

In this study, Cu~(2+) ions doped La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-δ) cathodes are prepared for use in solid oxide fuel cells (SOFCs). The maximum electrical conductivities of the La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.7)Cu_(0.1) O(3-δ) (438 S cm~(-1)) and the La_(0.6)Sr_(0.4)Co_(0.1)Fe_(0.8)Cu_(0.1)O_(3-δ_ (340 S cm~(-1)) discs are higher than that of the La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-δ) disc (LSCF; 81 S cm~(-1)) sintered at 1100℃ The substitution of Cu~(2+) over Fe~(3+) leads to a higher coefficients of thermal expansion (CTE), while the replacement of Co~(3+) by Cu~(2+) results in a lower CTE. Single cells with the La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-δ), La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.7)Cu_(0.1)O_(3-δ), and La_(0.6)Sr_(0.4)Co_(0.1)Fe_(0.8)Cu_(0.1)O_(3-δ) cathodes operating at 650 ℃ and 550 ℃ show similar ohmic resistance (Ro) values while the polarization resistance (R_p) values of the cells with the La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.7)Cu_(0.1)O_(3-δ) and a_(0.6)Sr_(0.4)Co_(0.1)Fe_(0.8)Cu_(0.1)O_(3-δ) cathodes are slightly lower than that of the single cell with the La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-δ) cathode, indicating that the Cu~(2+)-doped LSCF cathode exhibits a greater electrochemical catalytic activity for oxygen reduction. Maximum power densities of the cells with the La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-δ), La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.7)Cu_(0.1)O_(3-δ), and La_(0.6)Sr_(0.4)Co_(0.1)Fe_(0.8)Cu_(0.1)O_(3-δ) cathodes operating at 700℃ read respectively 1.07,1.15, and 1.24Wcm~(-2). It is evident that the doping of Cu~(2+) ions in LSCF is beneficial to the electrochemical performance of the cells.