Observation of a photocatalytic effect in the oxidation of CO adsorbed on Pt(100) and Pt(111) surfaces

The rate of oxidation, at 298 K, of CO adsorbed to high initial coverages on Pt(100) and Pt(111) surfaces is increased by irradiation by a VUV beam from a He resonance lamp. The effect is shown to be connected with the desorption of adsorbed CO, probably caused by secondary electrons produced by the resonance radiation. The effect on the rate is only observable under conditions in which O 2 adsorption is very slow and hence is probably attributable to (i) an enhancement of O 2 adsorption on the bare sites created by CO desorption and (ii) an increase in the number of CO islands as the CO coverage decreases, which produces a larger perimeter for reaction at the edge of the islands.