The performance and stability of La0.6Sr0.4Co0.2Fe0.8O3 (-) (delta) (LSCF) air electrode with Gd0.2Ce0.8O2 (-) (delta) (GDC) as an interlayer were tested in the Solid Oxide Electrolysis Cell (SOEC) mode. In order to study the stability and performance of the LSCF air electrode, an 8 mol%Y2O3-stabilized zirconia (YSZ) electrolyte supported on a Ni-YSZ fuel electrode was fabricated with and without a GDC interlayer, which was inserted between YSZ and LSCF. To determine the stability of the interlayer and find the optimum fabrication conditions, cells with the GDC interlayer were also co-fired at temperatures in the range of 1300-1500 degrees C and their performance was compared. Single cells were tested with an anodic polarization of 800 mA/cm(2) in 80% H2O + 20% H-2 at 800 degrees C. The cell without an interlayer showed a large increase in Ohmic Area Specific Resistance (ASR) from 0.09 Omega cm(2) to 0.16 Omega cm(2) during 50 h of operation due possibly to the observed delamination between the LSCF and YSZ. On the other hand, the cell with the interlayer showed a slower increase in Ohmic ASR from 0.14 Omega cm(2) to 0.153 Omega cm(2) with little delamination. The electrode polarization ASR of the cell with the interlayer also had a similar slower change, from 0.16 to 0.185 Omega cm(2), compared to that of the cell without an interlayer, from 0.143 to 0.35 Omega cm(2), after 50 h. The cell co-fired at 1400 degrees C had the smallest and most stable value of the total ASR for 100 h. (C) 2014 Elsevier B.V. All rights reserved.