Gas phase atomic hydrogen reacting with molecular and atomic oxygen to form water on the Pt(111) surface

Gas phase atomic hydrogen is more reactive than coadsorbed hydrogen during reaction with both adsorbed atomic and molecular oxygen on the Pt(111) surface. The increased reactivity of gas phase atomic hydrogen is demonstrated by complete conversion of all adsorbed molecular oxygen to water below 180 K. In contrast, coadsorbed hydrogen induces less water formation under similar conditions. Preferential hydroxyl formation is observed for low gas phase atomic hydrogen exposures as evidenced by the predominance of water formed by hydroxyl recombination at 200 K. Under these conditions the sharp reduction in the intensity of the molecular oxygen desorption peak at 150 K together with an increase in the atomic oxygen desorption peak at 800 K provide direct evidence for gas phase atomic hydrogen-induced O-O bond cleavage. Adsorbed atomic oxygen is also completely converted to water at 110 K even for low exposures of gas phase atomic hydrogen. (C) 1999 Published by Elsevier Science B.V. All rights reserved.