The effects of preadsorbed oxygen on the adsorption and decomposition of methanol on Ni(110)

Abstract

The adsorption and decomposition of methanol on a partially oxidized nickel surface, the Ni(110)-(2×1)O structure, has been studied using high resolution electron energy loss spectroscopy (HREELS) and thermal desorption spectroscopy (TDS). Methanol adsorbs molecularly at 80 K and multilayers of methanol can be condensed at this temperature. Molecular methanol is thermally unstable above ∼ 150 K and decomposes to a methoxy intermediate. Half of the chemisorbed methoxy desorbs by recombination in three desorption states with peak temperatures at 200, 240 and 300 K. Most of the remaining CH 3 O decomposes to CO and H 2 between 300 and 350 K, while a small amount is stabilized as a surface formate. HCOO, species. The formate decomposes into CO 2 and H 2 at 385 K. The presence of the surface oxygen affects the decomposition of methanol on Ni(110) in two ways: it stabilizes the methoxy group to higher temperatures, and induces the formation of a second intermediate, HCOO, above the methoxy decomposition temperature.