Reaction of gaseous oxygen with adsorbed carbon on Pt{110}(1x2)

The C oxidation reaction on Pt{110}(1 x 2) has been investigated using mole cular beam techniques. The reaction products are CO and CO2. As the surface temperature is increased from 550 to 750 K, the proportion of CO2 produced decreases from similar to 50% to < 1%. When oxygen first impinges on the s urface, the formation rate of CO is observed to rise immediately (less than or equal to 0.1 s), and then rise more slowly to a maximum before decreasi ng sharply as the C adlayer is depleted. The production of CO2 is initiated after a measurable delay. Angle-resolved product distribution measurements demonstrate that CO desorbs in a sharp lobe centered at an angle of 32 deg rees to the surface normal, fitted to cos(n)(theta-32), where n = 50 +/- 5. The C oxidation reaction site is identified with the (111) microfacets. It is concluded that two processes are operative, a Langmuir-Hinshelwood mech anism and a reaction in which CO is impulsively desorbed. (C) 2000 American Institute of Physics. [S0021-9606(00)70904-4].