Studying the Microstructure of Electrodes for Low-temperature Solid Oxide Fuel Cell and Electrolysis Applications

• Author / Creator

  Vafaeenezhad, Sajad

• Solid oxide fuel cells (SOFCs) is an important developing technology for energy conversion. This research was mainly focused on improving the fuel or air electrode of SOFCs in order to reduce the degradation rates and operation temperature. In chapters 3 and 4, a highly conductive Ni-yttria-stabilized zirconia (YSZ) anode was developed and tested in proton conductor and oxygen ion conductor SOFCs with improved stability and performance. In chapter 5, the composition and stability of an infiltrated praseodymium nickelate air electrode was studied. The infiltrated cathode was proven to be stable for over 250 h of a stability test in SOFC mode with no degradation.
  SOFCs – with proper modification - can also operate in electrolysis mode. Hydrogen is becoming an increasingly important medium for storage and transport of energy. It is possible to produce low-cost hydrogen using renewable energy and help balance the intermittent nature of renewable sources such as wind or solar. Solid oxide electrolysis cells (SOECs) have the highest conversion efficiencies compared to other alternatives such as alkaline or proton exchange membrane (PEM) electrolyzers. However, high steam content during high temperature electrolysis can degrade the Ni-YSZ fuel electrode. In addition, the air electrode can degrade due to anodic overpotentials. In chapter 6, the stability of the cell optimized for SOFC condition was studied in electrolysis mode. It was found out that the Ni-YSZ electrode suffered from Ni migration towards electrolyte and left behind large pores 100 μm away from the electrolyte. In addition, the distribution of relaxation time data showed an increase of the total polarization resistance of the cell due to degradation of the praseodymium nickelate air electrode in an anodic environment. The results of this study show further modifications of the SOFC electrodes are required to withstand electrolysis conditions.

• Subjects / Keywords

  • SOFC
  • SOEC
  • Electrolyte
  • Ni-YSZ
  • Microstructure
  • PNO
  • NNO

• Graduation date

  Fall 2022

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-yq9p-3e45

• License

  This thesis is made available by the University of Alberta Library with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.