Decomposition pathways of C1C4 alcohols adsorbed on platinum (111)

The adsorption and decomposition of methanol, ethanol, propan-1-ol, propan-2-ol and butan-1-ol has been studied on clean, and oxygen pre-covered Pt(111) surfaces. Temperature Programmed Reaction Spectroscopy (TPRS), Surface Potential Measurements (ΔV), UPS and XPS were used to characterise the adsorbed layer as a function of temperature. Each alcohol adsorbed into two states, a monolayer phase and a multilayer phase which were distinguishable by TPRS and Spectroscopy measurements. The monolayer alcohol adsorption heats increased sequentially from methanol to n-butanol (11.5–15 kcal mole−1). On the clean surface, less than 10% of the adsorbed monolayer dissociated, with 90% of the alcohol desorbing intact. Two competing dissociative pathways were observed: complete dissociation to adsorbed CO, H and C, and with propan-1-ol and butan-1-ol, scission of the CC bond nearest the CO group to form adsorbed CO, H and ethylidyne and propylidyne species respectively. The latter reaction probability was constant at 30% for n-propanol and n-butanol. In all cases the final desorption products were the parent alcohol, CO and H2 with carbon remaining on the surface for the higher alcohols. Atomic oxygen removed hydrogen from the alcohols as water but did not change the final reaction products.