Effect of Gd0.2Ce0.8O1.9 (GDC) infiltration on the performance and stability of La0.8Sr0.2MnO3 (LSM) oxygen electrodes on Y2O3-stabilized ZrO2 (YSZ) electrolyte has been studied in detail under solid oxide electrolysis cell (SOEC) operating conditions at 800 degrees C. The incorporation of GDC nanoparticles significantly enhances the electrocatalytic activity for oxygen oxidation reaction on LSM electrodes. Electrode polarization resistance of pristine LSM electrode is 8.2 Omega cm(2) at 800 degrees C and decreases to 0.39 and 0.09 Omega cm(2) after the infiltration of 0.5 and 1.5 mg cm(-2) GDC, respectively. The stability of LSM oxygen electrodes under the SOEC operating conditions is also significantly increased by the GDC infiltration. A 2.0 mg cm(-2) GDC infiltrated LSM electrode shows an excellent stability under the anodic current passage at 500 mA cm(-2) and 800 degrees C for 100 h. The infiltrated GDC nanoparticles effectively shift the reaction sites from the LSM electrode/YSZ electrolyte interface to the LSM grains/GDC nanoparticle interface in the bulk of the electrode, effectively mitigating the delamination at the LSM/YSZ interface. The results demonstrate that the GDC infiltration is an effective approach to enhance the structural integrity and thus to achieve the high activity and excellent stability of LSM-based oxygen electrode under the SOEC operating conditions. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.