(Invited) Unlocking a YSZ Degradation Mechanism in Solid Oxide Electrolysis Cells Triggered by High Operating Voltages

Le résumé fourni par la source

Solid oxide electrolysis cells (SOECs) can produce hydrogen by splitting water at high temperatures with a high electric efficiency, >95%. The long-term durability of SOEC components – the electrolyte, oxygen and hydrogen electrodes, interconnects – has been extensively studied to predict the SOEC stack life. In this work, SOECs were tested under a variety of potential operating scenarios while varying applied voltage, temperature, and steam content followed by post-test analyses using electron microscopy and atom probe tomography. When tested at voltages well above the thermoneutral voltage of ~1.3 V, while standard electrochemical techniques did not reveal obvious degradation in SOEC beyond the initial break-in period, high-resolution analyses uncovered intergranular and transgranular voids and cracks in the yttria-stabilized zirconia (YSZ) electrolyte. Thus, operating SOEC at high voltages, >1.45V, triggered YSZ degradation likely due to strain-vacancy interactions. By comparing SOECs with YSZ electrolyte and ceria barrier layers fabricated with and without high temperature sintering steps, the presence of either barrier/electrolyte interdiffusion layer or Ni precipitation was ruled out as triggers of void formation. This work provides valuable insights into the operation of real-time SOECs to enhance their long-term durability.

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