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

Paper SS1-MoA1
In-situ CV and XPS Evaluation of Tungsten Carbides as Alternative Electrocatalysts

Monday, October 31, 2005, 2:00 pm, Room 202

Session: Catalysis for the Hydrogen Economy
Presenter: M.B. Zellner, University of Delaware
Authors: M.B. Zellner, University of Delaware
J.G. Chen, University of Delaware
Correspondent: Click to Email
The purpose of this research is to examine the feasibility of using tungsten carbides (WC) and platinum modified tungsten carbides (Pt/WC) as direct methanol fuel cell (DMFC) and hydrogen fuel cell electrocatalysts. The motivation to study tungsten carbides stems from the fact that current fuel cells require the use of Pt or Pt/Ru anodes, which are expensive and easily poisoned by CO. The successful development of tungsten carbide electrodes as Pt/Ru substitutes can therefore positively influence the commercialization of DMFC and hydrogen fuel cell systems. Previously, reactions of CH@sub 3@OH, H@sub 2@O, H@sub 2@ and CO over single crystal and physical vapor deposited (PVD) thin film WC and Pt/WC surfaces have been studied with temperature-programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS). The results show that the carbide surfaces possess characteristics critical to application as fuel cell anodes. In particular, these surfaces are highly active toward the decomposition of CH@sub 3@OH and H@sub 2@O, and are able to desorb CO at relatively low temperatures. Recently, Pt-modified WC films along with PVD thin films of WC and W@sub 2@C have been tested for stability in an acidic environment and activity of methanol oxidation using an in-situ cyclic voltammetry (CV)/ X-ray Photoelectron Spectroscopy (XPS) test station. The tests show stability of WC to ~0.8 V wrt. NHE and a synergistic effect at monolayer Pt coverage, resulting in enhanced stability to ~1 V. Additionally, WC and Pt/WC surfaces show methanol O-H and C-H oxidation states, with the Pt/WC surface displaying greater methanol oxidation activity compared to WC or pure Pt foil.