Nb-doped La 0.6 Sr 0.4 FeO 3-δ as an electrolyte for intermediate-temperature solid oxide fuel cells.

It is one of the effective strategies to develop intermediate-temperature solid oxide fuel cells (IT-SOFCs) by looking for alternative electrolyte materials that can maintain or even improve current cell efficiencies while reducing operating temperature. In this study, by rationally introducing pentavalent Nb on the B-site of La 0.6 Sr 0.4 FeO 3-δ (LSFO), a serial of novel perovskite La 0.6 Sr 0.4 Fe 1-x Nb x O 3-δ (LSFNb x , x = 0.1, 0.2) with mixed electron-ion conduction is successfully prepared. The electrochemical mechanism and performance of the symmetrical IT-SOFCs with a single LSFNb x perovskite oxide as electrolyte are investigated. With the Nb doping, the structure stability of the LSFO is improved and the electronic conductivity decreases. La 0.6 Sr 0.4 Fe 0.8 Nb 0.2 O 3-δ (LSFNb20) is the most promising electrolyte of the three candidates as it has the best performance (735 mW cm -2 at 550 °C in a dry H 2 /Air atmosphere) and no short-circuiting problem. The applied voltage-response current curves demonstrate that the interface between the Ni-Ni 0.8 Co 0.15 Al 0.05 LiO 2-δ anode and LSFNb20 electrolyte can block electron conduction more efficiently and has a better promoting effect on protons, which is fundamentally due to the band energy alignment of the interface heterojunction. Our work highlights that LSFNb20 is a high-performance perovskite alternative to monolayer electrolytes.