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Carbon Dioxide Reduction on Gadolinia-Doped Ceria Cathodes

Green, Robert David
http://rave.ohiolink.edu/etdc/view?acc_num=case1232574534

Abstract Details

2009, Doctor of Philosophy, Case Western Reserve University, Chemical Engineering.
This work describes an investigation of CO-CO2 exchange on 40 mol% gadolinia-doped ceria (GDC) electrodes for potential application as a CO2 reduction cathode for the solid oxide electrolysis of CO2.A computational analysis was performed on the thick electrolyte cylindrical pellet test cell geometry to investigate the effects of this cell geometry on Electrochemical Impedance Spectroscopy (EIS) due to non-linear current distribution. The analysis showed the particular cell geometry selected does induce an error of 15% on the impedance measurements, but in a predicable linear manner. Additional parametric analyses indicate that impedance errors for the cylindrical cell geometry can be reduced by covering the faces of the pellet with the working and counter-electrodes, centering the reference electrode hole equidistant from working and counter-electrodes, or utilizing a reference electrode mounted at the midpoint edge of the pellet. A continuum-based model is described for equilibrium CO-CO2 exchange on a mixed-conducting electrode utilizing porous electrode theory. The resulting three-parameter model is expressed in terms of a characteristic resistance, a characteristic time constant, and a utilization thickness ratio, that can be related to physiochemical properties. EIS measurements were performed on the 40 mol% GDC electrodes on yttria stabilized zirconia (YSZ) electrolytes at 700-950 degrees C in reducing CO/CO2 atmospheres. Area-specific-resistance (ASR) values for this electrode were in the range of 0.8-37 ohm-cm2, about two orders of magnitude lower than measurements on Pt electrodes and slightly lower than data on Ni-YSZ electrodes in the literature under similar temperature and partial pressure of oxygen conditions. An analysis utilizing the continuum-based porous electrode model was performed to extract the vacancy diffusion coefficient and surface exchange rate coefficient as a function of temperature and partial pressure of oxygen, from the impedance results. The vacancy diffusion coefficient data agree well with published measurements of the tracer diffusion coefficient based on isotope profiling by secondary ion mass spectroscopy (SIMS), and conductivity measurements on 40 mol% GDC. The surface exchange rate coefficient values are a factor of 3 lower than published measurements of the surface reaction rate obtained from isothermal thermogravimetric relaxation and decrease with increasing partial pressure of oxygen.
Chung-Chiun Liu, PhD (Advisor)
Stuart B. Adler, PhD (Committee Member)
Uziel Landau, PhD (Committee Member)
Mark R. DeGuire, PhD (Committee Member)
J. Adin Mann, PhD (Committee Member)
254 p.
Chemical Engineering; Chemistry; Materials Science
carbon dioxide reduction; carbon dioxide electrolysis; Gadolinia-doped ceria; ceria; impedance spectroscopy; porous electrode model; electrode kinetics; exchange rate; vacancy diffusion coefficient; thermodynamic factor

Recommended Citations

Citations

  • Green, R. D. (2009). Carbon Dioxide Reduction on Gadolinia-Doped Ceria Cathodes [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1232574534

    APA Style (7th edition)

  • Green, Robert. Carbon Dioxide Reduction on Gadolinia-Doped Ceria Cathodes. 2009. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1232574534.

    MLA Style (8th edition)

  • Green, Robert. "Carbon Dioxide Reduction on Gadolinia-Doped Ceria Cathodes." Doctoral dissertation, Case Western Reserve University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=case1232574534

    Chicago Manual of Style (17th edition)

case1232574534
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© 2009, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.