CO adsorption and oxidation on oxygen precovered Cu(110) at 150 K: Reactivity of two types of adsorbed atomic oxygen determined by scanning tunneling microscopy

Scanning tunneling microscopy (STM) was used to investigate the reaction of carbon monoxide with atomic oxygen on Cu(110) in the steady state at 150 K. Oxygen dosed at 150 K reacts with copper atoms on the terraces to form -Cu-O- pseudomolecules 2-7 units long, in contrast to oxygen dosed at 300 K which forms long -Cu-O- chains in an islanded p(2x1) structure. Adsorbed CO forms regularly spaced stripes on the clean surface regions along the (1(1) over bar0$) direction between the p(2x1) oxide islands, perpendicular to the -Cu-O- chains in the coadsorbed p(2x1) oxygen islands. When dosed onto an oxygen precovered surface at 150 K, CO does not react with either p(2x1) oxygen or the pseudomolecules, presumably because both forms of oxygen are too strongly chemisorbed. However when the surface, partially covered with p(2x1) oxide and coadsorbed CO, is exposed to oxygen, the CO(a) reacts to form CO2. More weakly bound atomic oxygen that is a precursor to chemisorbed oxygen in the form of either the CO the pseudomolecules or the p(2x1) oxide appears to be more reactive with CO than chemisorbed oxygen.