Reaction of gaseous oxygen with adsorbed carbon on Pt{110}(1×2)

The C oxidation reaction on Pt{110}(1×2) has been investigated using molecular 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 ∼50% to <1%. When oxygen first impinges on the surface, the formation rate of CO is observed to rise immediately (⩽0.1 s), and then rise more slowly to a maximum before decreasing 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° to the surface normal, fitted to cosn(θ−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 mechanism and a reaction in which CO is impulsively desorbed.