X-ray absorption and electrochemical studies of direct methanol fuel cell catalysts

Technical Report · Tue Dec 31 04:00:00 EST 1996

DOI:https://doi.org/10.2172/460321· OSTI ID:460321

Zurawski, D. J.; Aldykiewicz, Jr., A. J.; Baxter, S. F.; Krumpelt, M. ^[1]

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1. Argonne National Lab., IL (United States)

In order for polymer electrolyte fuel cells to operate directly on methanol instead of hydrogen, a distinct advantage for portable applications, methanol oxidation must be catalyzed effectively in the acidic environment of the cell. Platinum-ruthenium and platinum-ruthenium oxide are generally considered to be the most active catalysts for this purpose. The presence of ruthenium significantly enhances the activity of platinum in these catalysts, for reasons not yet fully understood. We are using X-ray absorption spectroscopy (XAS) and electrochemical techniques to evaluate the mechanisms proposed to account for this enhancement in order to further improve the catalyst`s activity. We are considering three enhancement mechanisms. An intermediate in the oxidation of methanol on platinum is carbon monoxide and its oxidation is the rate-determining step in the overall oxidation mechanism. It has been proposed that ruthenium facilitates the removal of carbon monoxide from the platinum surface. First, it has been proposed that ruthenium decreases the strength of the platinum-carbon monoxide bond. Carbon monoxide bonds to the catalyst by interacting with the d-band of platinum, therefore a change in the d-band occupancy of platinum as a result of alloying may influence the bond strength of carbon monoxide. Another proposed enhancement mechanism involves lowering of the potential for the formation of the CO-oxidizing species. Finally, the binary catalysts may have a structure which is more conducive to the methanol dehydrogenation and carbon monoxide reactions. Based on these three proposed enhancement mechanisms, a goal of this study is to correlate catalyst electronic properties, structure, and oxidation state with the performance of proton-exchange membrane (Nafion) direct methanol fuel cells.

• Research Organization: Fuel Cell Seminar Organizing Committee (United States)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 460321
• Report Number(s): CONF-961107--Absts.; ON: TI97001494
• Country of Publication: United States
• Language: English

Related Subjects

30 DIRECT ENERGY CONVERSION
36 MATERIALS SCIENCE
66 PHYSICS
ABSORPTION SPECTROSCOPY
ALCOHOL FUEL CELLS
CATALYTIC EFFECTS
ELECTROCATALYSTS
ELECTRONIC STRUCTURE
METHANOL
OXIDATION
PLATINUM
RUTHENIUM
SPECTRA
VALENCE
X RADIATION