In this work, a YSZ electrolyte based solid oxide cell (SOC) with La0.6Sr0.4Co0.2Fe0.8O3-delta-Gd0.1Ce0.9O2-delta (LSCF6428-GDC) composite oxygen-electrode and a barrier layer of GDC between the electrolyte and oxygen electrode was fabricated and its performance was investigated while operating in fuel cell mode and steam/CO2 co-electrolysis mode in 700-850 degrees C range. The distribution of relaxation times (DRT) analysis of the electrochemical impedance spectroscopy (EIS) data was employed to isolate the contributions of electrode polarization processes. The reversibility of SOC was tested during the SOFC and steam/CO2 co-electrolysis operations at 800 degrees C. It was observed that at low current densities the current-voltage (i-V) curves showed good continuity across the open circuit voltage (OCV) but minor fluctuations in the SOC performance were observed at the higher current densities, which could be due to the gas-diffusion limitation of the reactants inside the electrodes or the microstructural changes occurring due to the electrode degradation. (C) 2015 The Electrochemical Society. All rights reserved.