Electrolyte degradation in anode supported microtubular yttria stabilized zirconia-based solid oxide steam electrolysis cells at high voltages of operation

• Published in: Journal of power sources Vol. 196; no. 21; pp. 8942 - 8947
• Main Authors: Laguna-Bercero, M.A., Campana, R., Larrea, A., Kilner, J.A., Orera, V.M.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01.11.2011; Elsevier
• Subjects: Alternative fuels. Production and utilization; Applied sciences; Degradation; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Electrolysis; Electrolytes; Electrolytic cells; Energy; Energy. Thermal use of fuels; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Fuel cells; Fuels; High voltages; Hydrogen; Hydrogen production; Microtubular; Reduction (electrolytic); SOEC; SOFC; Solid oxide steam electrolyser; Steam electric power generation; Yttria stabilized zirconia; Zirconia; Zirconia; Microtubular; SOEC; Solid oxide steam electrolyser; Hydrogen production; SOFC; Stabilized zirconia; Water vapor; Solid oxide fuel cell; Degradation; Zirconium oxide; Electrolyte; High voltage; Anode support; Electrolysis cell
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2011.01.015

Degradation of solid oxide electrolysis cells (SOECs) is probably the biggest concern in the field of high temperature steam electrolysis (HTSE). Anode supported, YSZ-based microtubular solid oxide fuel cells (SOFC) have been tested in fuel cell mode and also at high voltages (up to 2.8 V) under electrolysis mode. At high steam conversion rates the cell voltage tends to saturate. Our hypothesis is that this effect is caused by the electroreduction of the thin YSZ electrolyte which induces electronic conduction losses. YSZ reduction increases the cathode activity and reduces cathode overpotential. Operation of the cell in severe electrolyte reduction conditions induces irreversible damage at the YSZ electrolyte as observed in SEM experiments by the formation of voids at the grain boundaries of the dense YSZ electrolyte. Evidence of this damage was also given by the increase of the ohmic resistance measured by AC impedance. Signs of electrolyte degradation were also found by both EDX analysis and micro-Raman spectroscopy performed along a transverse-cross section of the cell. The observed oxygen electrode delamination is associated to the high oxygen partial pressures gradients that take place at the electrolyte/oxygen electrode interface.