AVS 52nd International Symposium
    Surface Science Monday Sessions
       Session SS1-MoA

Paper SS1-MoA2
Development of a High Temperature Electrochemical Reactor with Differential Electrochemical Mass Spectrometry for Kinetic Rate Analysis of Methanol Oxidation

Monday, October 31, 2005, 2:20 pm, Room 202

Session: Catalysis for the Hydrogen Economy
Presenter: L.M. Roen, University of Washington
Authors: L.M. Roen, University of Washington
E.M. Stuve, University of Washington
Correspondent: Click to Email
Direct methanol fuel cells have nearly the same potential as hydrogen fuel cells, ~1.2 V, though practical implementation has been limited by the kinetics of methanol oxidation. A full Langmuir-Hinshelwood model was previously developed@footnote 1@ in order to ascertain the kinetic rates of each elementary step of methanol oxidation on platinum. The strongest criticism of this model was its neglect of partial oxidation products. In addition to the empirical approach, we are collaborating with a theoretical group using Density Functional Theory to predict the kinetics rates from first principles. Experimentally, we need 4 independent measurements at different temperatures to find the kinetic rates and activation energies. The experimental system was designed to meet several requirements: (1) clean electrolyte environment, (2) no loss of potential control between measurements, (3) heating control from room temperature to 95°C, (4) quantitative detection of CO@sub2@, and, (5) minimal time delay for detection of volatile species. We have successfully constructed an electrochemical microreactor with on-chip heating attached to a differential electrochemical mass spectrometer (DEMS) to meet these requirements. Expected results of the measurements are kinetic rate constants, activation energies, and Tafel slopes for five elementary steps in the methanol oxidation process; direct oxidation to CO@sub 2@, series oxidation of CO to CO@sub 2@, accumulation of the CO intermediate, incomplete oxidation of methanol, and adsorption of methanol; over temperature, potential, and concentration ranges of 22 - 100°C, 0.2 - 0.6 V@sub rhe@, and 0.01 - 5 M respectively. @FootnoteText@ @footnote 1@ S. Sriramulu, T.D. Jarvi, E.M. Stuve, Reaction mechanism and dynamics of methanol electrooxidation on platinum(111), J. Electroanal. Chem. 467 (1999) 132-142.