Performance and Degradation of Solid Oxide Electrolysis Cells in Stack

ASolid Oxide Electrolysis (SOE) short stack consisting of anode-supported cells (ASCs in fuel cell mode) was assembled in JULICH's F10-design. ASCs are based on Ni/8YSZ (8 mol-% yttria-stabilized zirconia) with an LSCF air electrode (La0.58Sr0.4Co0.2Fe0.8O3-delta) and 8YSZ electrolyte. A gadolinium-doped ceria (GDC) (Ce0.8Gd0.2O1.9) barrier layer was deposited between 8YSZ and LSCF by means of physical vapor deposition (PVD). The stack was mainly characterized in a furnace environment in both fuel cell and electrolysis modes, with 50% humidified H-2 at 700 and 800 degrees C. An endothermic long-term electrolysis operation was carried out at 800 degrees C with a current density of -0.5 Acm(-2) and steam conversion rate of 50%. After 2300 h of operation, the stack showed an average voltage degradation rate of 0.7%/kh. Electrochemical impedance spectroscopy (EIS) and analysis of the distribution function of relaxation times (DRT) showed that the degradation was primarily due to the increase in ohmic resistance. (C) 2015 The Electrochemical Society. All rights reserved.