Oxygen chemisorption on Au(1 1 0)-(1×2) II. Spectroscopic and reactive thermal desorption measurements

Electron bombardment of physisorbed and condensed oxygen molecules on Au(1 1 0)-(1×2) at 28 K produces chemisorbed atomic oxygen. The latter was investigated with UV photoelectron spectroscopy (UPS) as well as with work function (ΔΦ) and reactive thermal desorption measurements (RTDM). UPS reveals that the electronic structure of chemisorbed oxygen bears a strong resemblance to that of gold oxide, Au2O3. At monolayer coverage, chemisorbed oxygen leads to a work function increase of 0.9 eV, indicating charge transfer from gold to oxygen. Coverages beyond one monolayer (which can be associated with gold oxide) have only little influence on the work function. Chemisorbed oxygen reacts vigorously with carbon monoxide even below 100 K. The reaction rate reaches a maximum around 175 K and depends on the instantaneous, but also on the initial oxygen coverage. At 175 K and an O coverage of 0.45 ML, we found a CO/CO2 conversion probability of 0.07.