The adsorption of oxygen on the stepped Pt(S)-[9(111) × (111)] face

The adsorption of oxygen on the stepped Pt(S)-[9(111) × (111)) face has been studied by flash desorption, LEED and AES. On adsorbing oxygen the (1 × 1) LEED pattern of the clean face was transformed into a (2 × 2) pattern. A lower limit of the initial sticking coefficient of 0.06 and a saturation coverage of approximately 0.5 monolayer were determined. The flash desorption spectra exhibited two not completely resolved desorption maxima. From the peak temperatures the activation energies of desorption were estimated to be 41 and 49 kcal/mole. Under the same experimental conditions some experiments were done on a smooth (111) Pt face. However, the results did not differ significantly from those obtained on the stepped surface. In addition on the smooth (111) face the adsorption of oxygen activated in a high frequency discharge was studied. Oxidation was not observed beyond the chemisorption layer which is formed from molecular oxygen.