Oxygen reduction on platinum : an EIS study
Name
426040929-MIT.pdf
Description
Full printable version
Size
2.38 MB
Format
Adobe PDF
Checksum (MD5)
354e8741bec7de5690ec8e575d047fc1
Author(s)
Golfinopoulos, Theodore
Advisor(s)
Yang Shao-Horn.
Date Issued
2009
Publisher
Massachusetts Institute of Technology
Abstract
The oxygen reduction reaction (ORR) on platinum over yttria-stabilized zirconia (YSZ) is examined via electrochemical impedance spectroscopy (EIS) for oxygen partial pressures between 10-4 and 1 atm and at temperatures between 475 and 700°C. Use of photolithographic techniques in electrode fabrication renders a precise geometry of the Pt electrodes. Circular electrode design leads to cylindrical symmetry so that models may be applied exactly to the experimental geometry. Interpretation of EIS spectra is carried out by reducing and then extending existing models, and is consistent with the postulate that ORR is rate-limited jointly by two surface chemical processes, namely, sorption/dissociation of molecular O₂ into O[delta]- a over Pt, as well as surface diffusion. Further, the novel experimental design, in conjunction with streamlined analysis techniques, provides accurate surface characterization within the electrochemical environment and allows for a more transparent comparison to relevant literature data. An adsorption coverage isotherm is extracted, and the surface diffusion coefficient is obtained for a number of experimental conditions. Extracted diffusivities fell between 2 x 10-2 and 2 x 10-7 cm2/s, in agreement with literature values for the indicated temperature range.
Description
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Vita.
Includes bibliographical references (p. 197-200).
Subjects
Electrical Engineering and Computer Science.
MIT Department
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
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