AVS 46th International Symposium
    Surface Science Division Tuesday Sessions
       Session SS2-TuM

Paper SS2-TuM2
Vacuum and Electrochemical Characterization of a Model Pt(111) Catalyst Modified with Vapor-deposited Ru

Tuesday, October 26, 1999, 8:40 am, Room 607

Session: Model Catalysts
Presenter: D.S.W. Lim, University of Washington
Authors: D.S.W. Lim, University of Washington
T.H. Madden, University of Washington
V.K. Medvedev, University of Washington
E.M. Stuve, University of Washington
T.J. Jarvi, United Technologies Research Center
Correspondent: Click to Email
A practical liquid fuel cell anode catalyst must oxidize fuel in the presence of adsorbed carbon monoxide (CO), whether the actual fuel is methanol in the direct methanol fuel cell, or hydrogen from reformed hydrocarbons. While platinum (Pt) exhibits the greatest reactivity for fuel oxidation, it alone is unable to oxidize CO at potentials low enough to be practical. Pt modified with ruthenium (Ru) can however oxidize CO at lower potentials, although the details of the Ru enhancement have not yet been established. Also, the lack of reproducible performance of both model and industrial Pt / Ru fuel cell catalysts indicates that the preparation / processing effects on catalyst structure and performance have not been adequately assessed. In this work, a Pt(111) surface is modified with Ru via physical vapor deposition and characterized in ultra-high vacuum using AES, LEED, and TDS. The crystal is then transferred directly to an electrochemical cell where blank and methanol-oxidation voltammetry are performed. Early results using an industrial electron-beam Ru deposition source suggest simultaneous multi-layer growth of the Ru adlayer on Pt(111) at room temperature. Room temperature blank voltammetry indicates new features in the low-potential region due to Ru on Pt(111). Methanol-oxidation voltammetry indicates reduced peak currents due to lack of dissociative adsorption of methanol on surface Ru at room temperature. These electrochemical characteristics due to Ru on Pt(111) can largely be reversed by a mild 300 deg C anneal in vacuum. We recently developed a small electron-beam Ru deposition source in our lab which allows highly precise Ru deposition under good vacuum conditions. More detailed vacuum and electrochemical characterization using this source for the Ru / Pt(111) system will be discussed. This work was supported by the Office of Naval Research, the National Science Foundation, the Link Foundation, and the University of Washington.