THE REACTION OF FORMIC-ACID WITH CLEAN AND WATER-COVERED PT(111)

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 CO2 and H2 exclusively at low exposure. At higher exposure, molecular formic acid begins to desorb at 200 K; simultaneously, the yields of CO2 and H2 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. © 1990.