Dual-path mechanism for catalytic oxidation of hydrogen on platinum surfaces

The catalytic formation of water from adsorbed hydrogen and oxygen atoms on Pt(111) was studied with scanning tunneling microscopy and high resolution electron energy loss spectroscopy. The known complexity of this reaction i s explained by the strongly temperature dependent lifetime of the product H 2O molecules on the surface. Below the desorption temperature water reacts with unreacted O adatoms to OHad, leading to an autocatalytic process; at h igher temperatures sequential addition of H adatoms to O-ad with normal kin etics takes place.