A novel perovskite oxide Ba0.9Co0.5Fe0.4Nb0.1O3-delta (BCFN) was prepared and characterized as oxygen electrode for solid oxide electrolysis cells (SOECs) using La0.8Sr0.2Ga0.83Mg0.17O3-delta (LSGM) as electrolyte. Symmetrical half-cell study shows that the polarization resistance of BCFN is only 0.08 Omega cm(2) at 750 degrees C in air. Electrochemical impedance spectra and voltage-current curves of the electrolysis cell with the configuration of BCFN vertical bar LSGM vertical bar La0.4Ce0.6O2-x vertical bar Ni-Ce0.9Gd0.1O1.95 were measured as a function of operating temperature and steam concentrations to characterize the electrolysis cell performances. Under an applied electrolysis voltage of 1.5 V, the maximum consumed current density increased from 0.835 A cm(-2) at 700 degrees C to 3.237 A cm(-2) at 850 degrees C with 40 vol.% absolute humidity (AH), and the hydrogen generation rate of the cell can be up to 1352 mL cm(-2) h(-1) with 40 vol.% AH at 850 degrees C. Further, the electrolysis cell has showed very stable performance during a 200 h short-term electrolysis testing, indicating that BCFN can be a very promising candidate for the oxygen electrode of SOECs using LSGM electrolyte. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.