The spatial distribution of product desorption in the oxidation of carbon monoxide on platinum (110)(1×2) reconstructed surfaces

Abstract

The spatial distribution of the desorption of carbon dioxide produced on platinum (110)(1×2) reconstructed surfaces was studied in the wide range of the reactant coverages by means of angle-resolved thermal desorption and low-energy electron diffraction. Heating the surface covered by oxygen atoms and carbon monoxide yields four peaks in the CO2 formation: P1-around 400 K, P2- (300 K), P3- (250 K), and P4-CO2 peaks (170 K). The desorption of each CO2 indicated a sharp angular distribution collimated along the bulk surface normal in the [11̄0] direction. On the other hand, the desorption of P1-and P2-CO2 produced at small CO coverages showed two-directional desorption collimated at either about +23 or −23 degrees off the bulk surface normal in the [001] direction. It indicates that the reactive desorption takes place on declining terraces of the reconstructed plane. The desorption of P3- and P4-CO2, and also of P2-CO2 produced at high initial CO coverages, showed a single peak in the angular distribution curve in the same direction, which was collimated along the bulk surface normal. This suggests that the reconstruction is at least partly lifted during heating procedures, and CO2 is formed on the nonreconstructed as well as the reconstructed plane. It was supported by low-energy electron diffraction observations.