The reaction of formic acid with clean and water-covered Pt(111)

Abstract

We have studied the interaction of formic acid with clean and water-covered Pt(111) in vacuum, using the technique of thermal desorption. We find that formic acid dissociates on clean Pt(111), forming gaseous CO 2 and H 2 exclusively at low exposure. At higher exposure, molecular formic acid begins to desorb at 200 K; simultaneously, the yields of CO 2 and H 2 saturate. At twice this exposure, the 200 K state saturates and multilayer desorption begins in a state centered at 165 K. Coadsorbed water does not measurably influence formic acid adsorption and dissociation. Finally, water is displaced from its own normal, high-temperature state by formic acid. This displacement is never complete, suggesting that formic acid or its dissociation products may not completely exclude water from metal sites.