Bi-doped La2ZnMnO6 − δ and relevant Bi-deficient compound as potential cathodes for intermediate temperature solid oxide fuel cells

• Bi-doping and Bi-deficient compounds were synthesized.
• Oxygen species and mixed-valent Bi5 +/Bi3 + and Mn4 +/Mn3 + were determined by XPS.
• Bi-doping can improve the oxygen ionic transport.
• The Bi-deficient composition can further promote the oxygen ionic transport.

The effects of Bi-doping and Bi-deficiency of La2ZnMnO6 − δ as cathode on the electrochemical properties were studied through a complex of physical-chemical characterization. We synthesized a series of compounds via a Pechini route, and the phase purity was greatly influenced by the A-site composition. X-ray photoelectron spectroscopy (XPS) testified the state of oxygen species and the mixed-valent states of Bi5 +/Bi3 + and Mn4 +/Mn3 +. The polarization resistances (Rp) of La2ZnMnO6 − δ (LZM), La1.5Bi0.5ZnMnO6 − δ (Bi0.5) and La1.5Bi0.5 − xZnMnO6 − δ (Bi0.5 − x, x = 0.25) are 0.122, 0.102 and 0.076 Ω cm2 at 850 °C, respectively, which are low enough to fulfill the practical application. All the analytical results demonstrate that Bi-substitution on A-sites does promote conductive properties due to the existence of high ionic conductive Bi2O3 phase. In addition, Bi-cation-deficient compound can further improve the transport performance because of the coexistence of Bi2O3 and Bi-cation defects. Therefore, these Bi-doping and Bi-cation-deficiency in LZM compounds can be promising cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs).