Reactions of methanol and water over carbide-modified Mo(110)

The reactions of methanol and water over clean and carbide-modified Mo(110) have been studied using temperature-programmed desorption, high-resolution electron energy loss spectroscopy, and Auger electron spectroscopy. The product selectivity of methanol on unmodified Mo(110) is 84% toward complete decomposition and 16% toward the production of CO. After the Mo(110) surface is modified by carbon, the complete decomposition pathway decreases to 63%, with the remaining methanol dissociating to produce CO. The absence of a reaction pathway to produce methane on the C/Mo(110) surface is distinctly different from that on the C/W(111) and C/W(110) surfaces. On Mo(110), the amount of H2O undergoing dissociation is determined to be 0.25 molecules per Mo atom. Upon carbon modification, the activity of water decreases slightly to 0.20 molecules per Mo atom. These results indicate that the C/Mo(110) surface is more active toward the dissociation of H2O than either C/W(111) or C/W(110). Overall, the comparison of the current study to our previous investigations on C/W(111) and C/W(110) provides insights into the possible role of molybdenum carbides as promoters for tungsten carbide electrocatalysts in methanol fuel cell applications. (C) 2003 Published by Elsevier Science B.V.