Reactions of methanol on W(100) and W(100)-(5 × 1)C surfaces

The decomposition of methanol-OD was studied on W(100) and W(100)-(5 × 1)C surfaces by temperature-programmed reaction spectroscopy. Initial adsorption of methanol-OD on the clean W(100) surface resulted in the complete dissociation of the molecule into hydrogen, carbon, and oxygen (β-CO). Methane, methanol-OH, and formaldehyde were observed as additional products after the CO(β) states had been saturated. The W(100)-(5 × 1)C surface produced the same products with the addition of carbon dioxide, water, and methyl formate. Moreover, the carbide surface enhanced the selectivity for hydrocarbon formation by an order of magnitude compared to the clean surface due to the suppression of the dissociation of methanol to β-CO and H₂ on the carbon chemilayer. The reaction mechanism was explained in terms of three intermediates: methoxy, formate, and a surface complex comprised of methoxy radicals and trapped hydrogen atoms. The "trapped" hydrogen atoms were apparently stabilized by the methoxy intermediates.