Identification and quantification of oxygen species adsorbed on Pt(111) single-crystal and polycrystalline Pt electrodes by photoelectron spectroscopy.

We have positively identified oxygen species on Pt(111) single-crystal and polycrystalline Pt electrodes in N2-purged 0.1 M HF solution by X-ray photoelectron spectroscopy combined with an electrochemical cell. Four oxygen species (Oad, OHad, and two types of water molecules) were distinguished. The binding energies of each species were nearly constant over the whole potential region and independent of the single- or polycrystalline electrodes. The coverages, however, varied considerably and were dependent on the electrode potential. We have for the first time demonstrated clear differences in the surface oxidation processes for Pt(111) and polycrystalline Pt electrodes.