A novel thick-film electrolyte-supported cell is constructed to separate cathodic (fuel electrode) from anodic (air electrode) polarization resistance R-p under high electrolysis current in a solid oxide electrolysis cell (SOEC). R-p of the SOEC are measured in various fuel humilities (40, 60, 80% H2O + balance H-2) at temperature of 650-800 degrees C and also compared those of a solid oxide fuel cell (SOFC). Anodic R-p of La0.6Sr0.4Co0.2Fe0.8O3-delta (LSCF) is similar to 3 times larger than cathodic Rp of Ni-YSZ (yttria-stabilized zirconia) composite at all temperatures tested, so anodic polarization is the limiting factor of electrolysis performance. Degradation of polarization resistance also occurs mostly at the anode under electrolysis current (-800 mA/cm(2)). Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.