Performance and Degradation of Solid Oxide Electrolysis Cells in Stack

Abstract

A Solid Oxide Electrolysis (SOE) short stack consisting of anode-supported cells (ASCs in fuel cell mode) was assembled in JÜLICH’s F10-design. ASCs are based on Ni/8YSZ (8 mol-% yttria-stabilized zirconia) with an LSCF air electrode (La 0.58 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ ) and 8YSZ electrolyte. A gadolinium-doped ceria (GDC) (Ce 0.8 Gd 0.2 O 1.9 ) 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 °C. An endothermic long-term electrolysis operation was carried out at 800 °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.