LOW-TEMPERATURE CO OXIDATION TRIGGERED BY THE GAS-PHASE D ATOM INCIDENT ON PT(111) COVERED WITH O-2 AND CO

Exposing an O-2-saturated Pt(lll) surface at 85 K to a beam of D atom leads to desorption of O-2 and D2O. A series of post D-exposure therma l desorption spectra shows that D2O is produced by consecutive D-addit ion reactions via adsorbed OD intermediate,i.e., O-2(ad)-->O-D(ad)+ OD (ad)-->(D2O)-D-D(ad) +D2O(g). When CO is coadsorbed with O-2 On Pt(lll ) at 85 K, the incident D atom also induces prompt desorption of CO2 b ut not CO. We propose that CO is oxidized by the nascent hot O and OD formed in a highly exothermic initiation reaction D(g)+O-2(ad)-->DO2 not equal-->O(ad) + OD(ad) with an energy release of :similar to-4.6 e V before they become accommodated to the surface. Possible mechanisms for O-2 desorption are also briefly discussed. (C) 1998 American Insti tute of Physics.