Oxygen reduction on platinum : an EIS study

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.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2009

Author dc:creator

• Golfinopoulos, Theodore

Advisor dc:contributor.advisor

• Yang Shao-Horn.

• Electrical Engineering and Computer Science.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/46379

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/46379