Potential application of tungsten carbides as electrocatalysts

The reactions of methanol, water, and carbon monoxide over clean and modified tungsten carbide surfaces are studied by using temperature programmed desorption, high-resolution electron energy loss spectroscopy, and Auger electron spectroscopy. The carbide-modified W(l 11) surface is highly active toward the decomposition of methanol, with 55% going to complete decomposition, 31% to CO, and 14% to CH4. Additionally, the C/W(111) surface exhibits strong activity toward the dissociation of water. Furthermore, the desorption of CO from C/W(111) occurs at a relatively low temperature of similar to330 K. When modified by the presence of submonolayer Pt, the decomposition pathways of methanol are significantly altered. The presence of low-coverage Pt onto C/W(111) effectively inhibits the production of CH4, an undesirable side product in direct methanol fuel cells. The Pt-modified C/W(111) surface also remains active toward the dissociative of water. When C/W(1 11) is modified by oxygen, the surface retains significant activity toward water and methanol, and at the same time lower the CO desorption temperature to 242 K. Finally, the investigations on carbide-modified W(110) reveal minor structure sensitivity in terms of product selectivities, while the overall activity values of methanol and water on the two C/W surfaces are nearly identical. The results on the C/W(I 11), Pt/C/W(l 11), O/C/W(1 11), and C/W(1 10) surfaces are compared to those on the Ru(0001) and Pt(I 11) surfaces. (C) 2003 American Vacuum Society.