Understanding the phase stability of yttria stabilized zirconia electrolyte under solid oxide electrolysis cell operation conditions

Abstract

Solid oxide electrolysis cells (SOECs) have garnered interest as efficient systems for hydrogen production through water electrolysis. One critical limitation hindering the widespread adoption of this technology is the long-term degradation of electrodes. In addition, ensuring the durability of the electrolyte remains a significant challenge. This study delves into the degradation mechanism of yttria-stabilized zirconia (YSZ) with varying Y₂O₃ compositions under an applied electric potential. In a comprehensive investigation of the degradation behavior of YSZ electrolytes with Y₂O₃ doping ranging between 8 and 10 mol%, the 8YSZ composition exhibited a pronounced reduction in ionic conductivity compared to 9.5YSZ and 10YSZ. Although 8YSZ exhibits the highest ionic conductivity, it has been determined that, under SOEC operating conditions, a Y₂O₃ doping concentration exceeding 8 mol% is required for stability owing to the precipitation around the electrode induced by the electric field. Electrical analysis, X-ray diffraction, Raman spectroscopy, and transmission electron microscopy were utilized to assess the degradation behavior of the electrolyte. K-means clustering was applied to highlight the disorder in defects observed through energy-dispersive spectroscopy. This study elucidates the underlying mechanisms governing electrolyte degradation in SOECs and recommends optimal YSZ compositions for prolonged operation, considering thermal stability and durability under SOEC operating conditions.