Lanthanum strontium vanadate (LSV) was used as the cathode of a solid oxide electrolysis cell (SOEC) containing a yttria-stabilized zirconia (YSZ) electrolyte for the coelectrolysis of steam and CO2. Pd and CeO2 were added to the composite cathode, and the electrolysis mechanism in the coelectrolysis mode changed according to the type of catalyst in the LSV/YSZ composite cathode. The effect of steam on the coelectrolysis performance was investigated by varying the steam vapor pressure. The electrolysis performance under dry CO2 without steam degraded with time under electrochemical reduction conditions owing to the deactivation of catalysts. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.