Advanced Microstructure Optimization Strategies for High-Temperature CO2 Electrolysis: Infiltration and In-situ Exsolution

• Author / Creator

  Ding,Shaochen

• The solid oxide electrolysis cell (SOEC) has attracted increased attention in recent years due to its capability to reduce CO2 emissions in a highly efficient and environmentally sustainable fashion. Previous work in our group has fabricated an A-site Ce doped La0.7Sr0.3Cr0.5Fe0.5O3- (LSCeCrF) with gadolinium doped ceria (GDC) as the cathode material in SOEC by the conventional method. This material presents a satisfying electrochemical performance and good stability due to the presence of excessive oxygen vacancies, which constitute the strong CO2 adsorption ability of the material. However, the electrochemical catalytic activity is still limited by the catalyst specific area. Hence, the optimization of electrode microstructure is considered as a promising way to further improve the SOEC performance by increasing the active reaction area.
  In this thesis, LSCeCrF and GDC composite cathode was firstly fabricated by infiltration method, and the results were compared with one from our previous study with a conventional fabrication method. From analysis of laboratory results, it is evident that the infiltration method can effectively improve electrochemical performance of SOEC, with optimized microstructure of the cathode. Secondly, to further improve the catalytic activity for CO2 conversion, (La0.65Sr0.3Ce0.05)0.9(Cr0.5Fe0.5)0.85Ni0.15O3- (Ni-LSCeCrF)/GDC nanostructured cathode was fabricated by infiltration and in situ exsolution of highly active Ni-Fe alloy nanoparticles.
  The effects of electrode microstructure optimization on the electrochemical performance were investigated in the atmospheres of pure CO2, and mixture of CO2 and CO (CO2 mole fraction as 0.7). The Ni-LSCeCrF/GDC cathode shows significantly improved electrochemical performance, CO production rate, and Faraday efficiency for CO2 reduction in both atmospheres. Furthermore, collaboration with Ms. Wanying Pang, PhD student supervised by Professor Zhehui Jin, density function theory calculations were carried out to investigate the exsolution trends of transition metals on B-site of a perovskite lattice. The results show that Ni doping could reduce the segregation energy of Fe, revealing an alternative strategy of multiple elements doping to form active alloy by in situ exsolution.

• Subjects / Keywords

  • Microstructure Optimization
  • SOEC
  • In-situ exsolution
  • Infiltration

• Graduation date

  Spring 2020

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-e83e-4t89

• License

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