Studies of Perovskite-based Materials in Solid Oxide Fuel Cells: Anode Performance Optimization and Degradation Mechanism of Electrolyte

• Author / Creator

  Gao, Tong

• As an alternative energy generation device with higher efficiency compared to conventional devices, the solid oxide fuel cell (SOFC) has been widely investigated. However, the application of SOFC is seriously limited due to the difficulty of maintaining an effective balance between excellent performance and strong stability in operation.
  SOFCs can take advantages of fuel flexibility in their potential to use syngas or methane as the fuels. However, the conventional metallic anode catalyst suffers from carbon deposition problems while the perovskite material exhibits a poor performance when fuelled with light hydrocarbons. Therefore, this thesis focuses on enhancing catalytic performance, thermal stability and chemical stability of perovskite materials in syngas by infiltrating the porous substrate with nano-scaled catalysts such as Cu, CeO2 and Co. The results indicated that pre-infiltrating CeO2 into substrate enhanced the thermal stability of the dispersed metallic catalysts. Moreover, with the increase of the amount of catalysts infiltrated, the triple-phase boundary was enhanced until there was an excess amount of metal infiltration that reduced the active sites. The cell with a La0.3Sr0.2Ba0.1TiO3-δ (LSBT)/yttria stabilized zirconia (YSZ) anode infiltrated with 10.5 weight percent (wt%) CeO2, and 2 wt% Co exhibited excellent electrochemical stability, with only negligible degradation observed under 24-hours tests in syngas.
  The second focus of this thesis is the attempt to study the degradation mechanism of BaCe0.7Zr0.1Y0.2O3-δ (BCZY) discs. In a novel proton-conducting SOFC, BCZY is applied as the electrolyte because of its high proton conductivity. However, the mechanic properties and electrochemical properties of the BCZY material degrade severely at room temperature. To better understand the degradation mechanism, a number of characterization methods were used, such as scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA)-mass spectrometry (MS). The results demonstrated that H2O played a crucial role in initializing the degradation, and CO2 contributed to the subsequent degradation process which resulted in the formation of BaCO3. Based on this mechanism, solutions for preventing degradation when fabricating and storing BCZY discs can be designed.

• Subjects / Keywords

  • Electrolyte
  • Solid oxide fuel cells
  • Anode
  • Perovskite

• Graduation date

  Fall 2014

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R30V89Q2M

• License

  This thesis is made available by the University of Alberta Libraries 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.