The decomposition of methanol on the sulfur-modified Fe(100) surface

Abstract

Decomposition of methanol (CH 3OH) on sulfur-modified Fe(100) surfaces has been studied under ultrahigh vacuum (UHV) conditions, using temperature-programmed reaction spectroscopy (TPRS) and high-resolution electron energy loss spectroscopy (HREELS). Preadsorbed sulfur overlayers, prepared by thermal decomposition of CH 3SH, poison the decomposition of CH 3OH on the Fe(100) surface. The decomposition of methanol occurs by way of a methoxy (−OCH 3) intermediate on the sulfur-modified surface. The amount of methoxy intermediate formed in the decomposition process decreases as sulfur coverage increases. Preadsorbed sulfur atoms also modify the selectivity of the methanol decomposition. The formation of formaldehyde (H 2CO) is enhanced in a rather narrow sulfur coverage range, while the amount of carbon monoxide (CO) product decreases monotonically with increasing sulfur coverage. The effect of sulfur modification on the decomposition of methanol appears to be primarily a localized site blocking effect. Sulfur modification of the methanol decomposition on this surface is compared with that of the effect of oxygen modification.